Some heroes don’t wear capes, some are cloud software developers. Cloud software developers may not be that famous as the cloud software that they have created but thanks to them, we can now our files in our gadgets. Their job requires patience and does not require much physical movement. For busy cloud software developers, they usually don’t have much time to do household chores. Indeed, they really need to invest in house products that can make things easier and more convenient for them. Two of the most important household chore that these developers should always do are preparing their clothes and cleaning the house. Thanks to technology, removing wrinkles in clothes are now made easier by garment steamer and cleaning the floor also will not take much time with the help of steam mop.
If you are a cloud software developer who is always on the go and loves to travel, you should invest in a garment steamer now. Garment steamers are easy to use and be even brought anywhere and it works even better than irons. The boiling water to produce the steam is kept in a secure container. Just read the customers manual to find the most effective way to displace water to avoid accidents. Some texture vessels require a specific cooling period before opening the store for water substitution. With the convenience brought by garment steamers, do not leave home without it if you will be traveling.
It’s not difficult to steam clothes. To begin, you just have to apply steam to the upper surface of the garment to soften the texture using the flat surface. This will make a smooth finish even against the most stubborn wrinkles. The best thing about this garment steamer is its insignificant dangers compared to the usual irons that can consume unintentional contact. Old pressing strategies can damage or even dissolve sensitive textures. Even when clothes are hanging, they can be steamed. We know overall how traditional heated irons can damage, consume, burn or, in some cases, soften sensitive textures.
For sensitive textures, a vaporizer is suggested because its texture is delicate compared to that of conventional irons. These can be used to get rid of wrinkles shades, can be used adequately to clean your favorite lounger and to clean the shower sheet. Steamer gently sits in contact with the steam head through which wrinkles are expelled in seconds, leaving your clothes safe. It should not touch silk or velvet directly with the vaporous head. Some textures or clothes must be steamed from below. Steam will help loosen locks and eliminate wrinkles.
If you are a cloud software developer with pets or floors at home that is prone to dirt, you should have steam mops at home. Compared to the traditional mops, it makes the dirt and even hairs of your pets be removed easily by steaming and through its special features such as the pet hair strainer. Cleanliness at home is very important because it can also set your mood and productivity.
As a cloud software developer who spends much of your time thinking and analyzing at work, you should invest in some things that can help you make household chores not stressful. All these are good choices as these two products can add value to your life as a developer. You would not want to spend much time on removing wrinkles on your clothes or cleaning the floors than spending your time with loved ones and resting, don’t you.
Cloud storage is a friend of photographers. It is not a real cloud but a store mouth of data. Photographer has a variety of picture options as they don’t want to delete any photos. In this fact, cloud storage helps them in all circumstances. It has flowed in the internet world. It has removed storage difficulties a photographer daily face.
Cloud Storage: What is it?
The term cloud storage defines online data storage. It has that ability to transfer digital data in logic pools. It is different from physical storage as physical storage has physical existence, server cause, environment dependent, and many characteristics. On the other view, cloud storage offers storage to keep the data with more accessibility. It has more stability with high security.
Cloud storage presents co-located cloud service. It is known as API service with the full definition of web service application programming interface. Cloud storage is based on a huge virtual foundation. Its service can utilize through the off-premise protocol. This online storage system serves hosted object storage. Here’s the main summary of what cloud storage is:
– It is made from the distributed resource. The main foundation of this technology is a cooperative storage cloud design.
– This function contains high tolerant about the distribution of data
– Durability is the first thing to consider.
Cloud storage: Types for the photographer
Cloud storage has no limitation with hundred of the branch. For photographers, cloud storage has special service and diplomatic tech with high facilities.
Community web base cloud storage:
Uploading a photo with unlimited access power through any browser is known as community web-based clouds. For the unlimited ability civilian with photography skill needs to worry about nothing.
Local web-based cloud storage:
From a local user, when the user uploads some photo or files in some web pages. The photo is uploaded in the cloud through internet connections. The photographer needs to spend money as the quantity of storage. Google drive, Live drive are some of this software.
Private cloud storage:
Private cloud differs through user demand. A civilian can buy as much as he wants. It is expensive with lots of advantages. Private companies don’t buy storage as they rent it through cloud storage. In this process, the user can manually upload photos or files in cloud storage. Space bought by the user varies as use substances.
Other useful accessories for photographers:
Ambico tripod offers radical brace with maximum stability. It has quick release leg with lock system. This can sit up with full flexibility. Ambico tripod parts provide the best weight management and removal for the camera.
Cloud storage to save photos
There is a different cloud storage sharing company available in the market. They offer different values with most accessibility. But we need to choose one with the best service. The main purpose is to keep the photo. Some renowned cloud storage renters are:
Dropbox: Easy to use Stores any file type Proven legacy Expensive
Google Drive: Free productivity apps are thrown in Unlimited photos A photo assistant Can be daunting at first
Microsoft One drive: Free productivity suite was thrown in Cheaper 1TB storage than the rest Less photo-focused than the competition
Flicker: Free Unlimited storage with Flicker Pro Can’t store RAW files
Adobe creative cloud: Best one for photography issue
Cloud storage is indeed a very important tool for photographers as it gives the convenience of being to save photos in laptops without the worry that it may be lost. Investing in a cloud storage is a must nowadays.
You judge a company by the interior and exterior decor. Right from the furniture to the fittings, all these have an impact on the attitude of the clients towards the company. A cloud software company should invest in the best heavy-duty router tables from a renowned woodworking website to make a choice.
In as much as it deals with the tech field where most of the virtual clients are, their office design should have a positive impact just like the applications they develop.
Cloud storage is the current digital solution in the storage of data for both personal and commercial use. With the correct applications, be sure of an influx of clients fighting to have space on your storage platform.
Ask yourself the following questions
· As they wait for service from your office, how comfortable are they in the woodwork furniture?
· What is the outlook of your office desk?
· Are your fittings in line with the color scheme?
· Does your woodwork design add aesthetic value?
These are the guiding principles of the best office design for your cloud software company. Here are some of the ideas to achieve this goal.
As a company you have a company color, ensure you spray your woodwork design with the color theme in mind to enhance the welcoming effect as well as the vision and the goal of the company. Different colors portray different effect and all these should be portrayed in your company merchandise.
You have to utilize the office space without it being cluttered or too empty due to a poor arrangement. In the setting, ensure there is free movement and joints of the woodwork furniture are correctly tacked on the wall to enhance durability and avoid minor accidents within the office.
Creativity and uniqueness of the designs
As a cloud software company, you take pride in creativity and originality of the application, depict this in the office furniture and woodwork designs in the office. Use online tools and renowned woodworker to make designs that every visitor in your office never fails to notice. It will give you an upper hand in closing a business deal. “If they invest in the best office designs, what of the products?” a client laments. It gives a client a sense of professionalism and integrity in service delivery of your products.
Imagine of a cloud software company with a detergent as a cover picture. You get the confusion in the relevance of the theme. Why not place a computer in one of your woodwork designs to enhance the applicability of your products?
You can also portray your creativity in woodwork designs in the partitions of your office. If you lease a business premise without partition, it is time to portray your woodwork skills by enhancing its beauty through unique partitions.
Woodwork is a vintage skill that finds relevance in contemporary society. Although there are new methods, the incorporation of old designs still gives a cloud software company a facelift Despite the virtual nature of their work. Engage a professional woodworker or DIY projects.
Table tennis is an indoor game. It is an Olympic sport, played worldwide. It is also known a ping-pong in many countries. This game can be played between 2-4 players. It uses a tabled platform as its ground and a lightweight ball, the players hit the ball with rackets towards other opponents court and try to score. This game is governed by the worldwide organization international table tennis federation. This game is generally dominated by South-east countries like China, Taiwan, Chinese Taipei, Hong Kong. The sport tests the reflexes and speed of a person. By playing table tennis the players can develop high-speed hand-eye coordination. Nowadays these games have gained popularity in every place be it office, room, hostel, it can be played anywhere, anytime by anybody. The setup of the game is not much costly and can be easily deployed anywhere.
Benefits of playing table Tennis
Table tennis is very entertaining and recreational sports one can play it anytime, anywhere. He can
play it with his friends or even alone. The game is very beautiful and has many benefits in this modern world, this game helps in releasing stress, change the mood of the person. It also has benefits in developing good eye-hand coordination, improving the speed of a person, increases reaction time, keeps
the brain attentive all the time and makes it focused. However, playing this game with full concentration leads to both mental and physical exhaustion of a player. Hence it is required to play it lightly and in a surrounding where the brain can relax. It is often observed that players play music in the background while playing table tennis.
Benefits of Playing Music
By now playing any sports with full concentration for a long period of time can be tiresome and can exhaust you both mentally and physically. Hence it is required to employ other means to recreate and save yourself from exhaustion and enjoy the game. It is advised that one should play I turn with their friends to enjoy the game and relax by taking a break after a short period of time. However, if you want to play for a long period of time it is. It is often observed that the players play music in the background to keep your mind distracted and don’t get bored. This sports employees lots of stress on the mind, eye, and muscles involved in playing this games. After a short period of time, the player starts to become bored and tired and leaves the games. He cannot play for a long duration. Hence professional players employees playing music while training to stop getting bored.
It is observed that listening to music is relieves stress and changes the mood. Smooth and energetic music plays an important role in developing a person character in a positive way. Hence if you want to play for a long time or train hard then it becomes necessary to play energetic and positive music in the background. Because when you are practicing these hard on table tennis spent a lot of their time on the table. They practice for long duration. This practice helps them developing their mind and reaction time on their hands and other body parts. Hence it is necessary to think positive at that time because these practiced things get stored in your unconscious mind and once stored it is hard to change. Hence it is necessary to have positive thinking while practicing For that playing positive music which makes you
happy, gets you excited can help in improving your games and practice more. These music relaxes your mind and makes it feel happy and calm, due to this calmness you get to concentrate more, you don’t feel bored and start paying more attention and enjoy the game, which in turn improves your skills both
mentally and physically. Hence it is advised to make the playlist of the song which makes you happy and calm. And play them whenever you go to play table tennis.
With all the above mentioned benefits of playing table tennis with music, it is very important for table tennis players and coaches to invest in a good file system. A file system is a system in which the files are saved or stored. Without it, music files will be saved in any computer or any storage hardware like hard drive or flash drive. I experience how hard at practicing against myself but practicing alone with music makes me feel pumped. We are now living in a modern world where everything is online and using gadgets and this is another reason why file systems are very important.
Most of us love taking part in outdoor games and recreation. However, cold weather in certain periods of the year such as the winter makes it hard enjoy the outdoor games. This is the time to enjoy the indoor games. On the other hand, some individuals prefer the indoor games. If you enjoy indoor games, then the ping-pong or table tennis game is a great choice. The ping-pong is similar to the tennis game only that you play it on a table instead of a court. The game has a net at the center, which marks the boundary between you and your opponent.
The ping-pong game is a great game to spend quality time with your family. If you have children in your home, it is important to understand that they desire to spend time with their parents. Family time is important when it comes to the development of your children both intellectually and psychologically. Besides assisting in the development of your children, it also helps in optimizing your family bonds. This article will discuss some of the benefits playing ping-pong game with your family.
One of the benefits of playing this game is that it offers your children with learning opportunities. This is a great family game fun at home provides you with an entertaining way to learn new skills. There are many essential skills and benchmark concepts that you pass to your children when playing this game. Fist this game will provide your kids with the ability to optimize their ability to recognize certain words and letters which in turns improve your kid is reading skills. When playing this game, your child will also benefit from color recognition and improvement of visuals.
Besides enhancing your children intellectual growth, this game will also improve your child social skills. Since the game requires you to communicate verbally, your child will learn how to express themselves when out with their children. By interacting with other family members, the game will provide the child with an opportunity to open up and communicate openly with other members of the family. This will foster relationship within the family unit and build closer bonds between you and your family.
Besides bringing your family together, your child will learn how to play a game that he/she enjoys. Through the exercise, your child will gain all the basic knowledge of the game, and this can give them the skill they need to compete with other kids. This will also give your child a favorite pastime activity, and this can keep them occupied. Additionally, ping-pong game will help the children to exercise. With the rise of obesity in children, playing ping-pong is very helpful when it comes to exercising. Exercise will keep their body fit and avoid the diseases that are associated with being overweight.
Today’s technology has enhanced the convenience of doing things. You can record the game and store it so that you can remember the fun time you spent with your family. Today there are many storage devices that you can keep the data. You can decide to keep the data on your computer’s hard disk or memory cards. However, your computer can crash, and this may make you lose all your data. The Cloud storage can also save Ping-pong match video. Saving the video in cloud storage will allow you to keep it safe and you can retrieve it anytime you want. This technology allows you to save your videos for a lifetime without any risk of losing them.
A jacket for a motorcycle is a bike gear with numerous functions. The work of a cloud storage developer involves long hours of sitting and being indoors just to ensure the programming language is on point without disappointing the clients. Riding a motorcycle is an unwinding activity to allow him to relieve anxiety and relax. A jacket comes in handy as a protective gear and a safety measure.
In some states, you are not allowed to ride without a jacket. Imagine of an impact, apart from the helmet the upper limbs are protected by the jacket made from a light mesh material for summer riding. The outdoor event causes health challenges, especially during the cold season. The extreme exposure of your chest to cold might cause asthma, pneumonia and other health-related conditions.
Yes, you want to have an outdoor activity, and you feel riding is the best option. A helmet, boots, and a long pant are protective gears for all seasons.
What entails the best motorcycle jacket for a cloud storage developer?
Choose a jacket made from the material with the ability to regulate heat and temperature to enhance comfortability. The inner lining should be made of cotton renowned for this feature such that when it is very cold, the heat is absorbed towards the skin to keep the rider warm. When it is hot, it should also radiate the heat away from the body.
Are you able to ride during the rainy season and still have fun? This is only possible with a jacket with a waterproof lining, to keep you warm despite the winter season or rainy season. In addition, the waterproof ability allows you to adventure and ride in stormy and muddy waters without a hindrance.
What happens when you are in a rugged landscape? How comfortable will you be in the jacket? Ensure the material has a shockproof ability to withstand rough terrain at the same time the sliding material should protect you from bruises in the case of an impact or a fall.
The lighter the motorcycle jacket, the better the coziness. This is possible with a light material which does not compromise on the safety. The jacket has then two to three layers, each of the layers has a purpose with aesthetic value.
Riding in the dark is inevitable. A mechanical problem might arise or rather get lost in the course of your riding adventure. A good motorcycle jacket should have a reflector as a safety measure especially when riding on a busy highway. It alerts other motorists of your presence on the road.
Despite the safety and protection, never compromise on your taste of color. You are at liberty to choose a color of choice to match your passion and enhance your sense of fashion when riding.
Whether a cloud software developer rides as a workout plan or for fun or adventure, a jacket is a must-have clothing for protection and safety for him or her as well as prevent endangering other motorists and road users.
My previous dog food post did generate a couple of requests for more detailed instructions on how to build your own private cloud storage repository, so here goes.
First, you need to have a server somewhere that will always be on, or at least on as much of the time as you want to access your cloud storage. I happen to have a server in the Rackspace Cloud that I leave running for various purposes at $10/month. If you already have a cloud server or VPS that you’re running somewhere, or a home/work machine, that works fine too.
Next, you need to be running GlusterFS on your server and clients. There are already pre-packaged versions available for some Linux distributions, though some are more current than others. For example, Fedora is at 3.1.3 which is pretty close to current, while Ubuntu is at 3.0.5 which is simply too old to be useful. Downloads are also available from Gluster themselves and elsewhere. However, you’re highly likely to run into a problem with many of the pre-packaged versions. Prior to 3.1.4, the servers would not accept connections from non-privileged ports and if you’re using any sort of NAT/tunnel/VPN you’ll probably be assigned just such a port. At least in 3.1.4, they added options to override this misguided code (which doesn’t even check the port’s privilege status the right way BTW) but my choice was to remove it entirely and build my own RPMs. I’ll provide patches and fixed RPMs soon; bug me if I forget. Anyway, install whatever 3.1+ version you want and move on to the next step.
At first, you’ll want to create your volumes and start your server-side daemons the “normal” way, something like this.
# mkfs -t ext4 /dev/sdwhatever # mkdir -p /bricks/mycloud # mount -o noatime,user_xattr /dev/sdwhatever /bricks/mybrick1 # gluster volume create mycloud my.external.ip.address:/bricks/mybrick1 # gluster volume start mycloud
At this point, you would actually be able to mount the “mycloud” volume from any GlusterFS client, unless you have firewall issues (which you often will in a public cloud including Rackspace). Here’s one simple way to get around that, though I actually don’t recommend this method for reasons I’ll get to in a moment.
# netstat -lpn | grep glusterfsd # iptables -I INPUT -p tcp --dport 24009 -j ACCEPT
24009 is just the port I happened to get. Also, you’d probably want to make the IP tables rule more specific to the hosts you use, save it as part of your private config, yadda yadda. However, the reason you probably don’t want to do this is that it provides no security at all. Instead, you’ll want to run this through some sort of tunnel, and in that case, you’ll effectively be making a local connection to the server. Here’s how you’d do it with ssh.
# ssh -L24009:localhost:24009 email@example.com
The other part of this is avoiding some of Gluster’s port-mapping silliness. Grab the client-side “volfile” describing the mount from /etc/glusterd/vols/mycloud/mycloud-fuse.vol and copy it to whatever machines you’ll be mounting on. Edit the “protocol/client” part of the copy to look something like this:
volume mycloud-client-0 type protocol/client option remote-host localhost option remote-port 24009 option remote-subvolume /bricks/mybrick1 option transport-type tcp end-volume
Now your mount command can change something like this.
# mount -t glusterfs my.cloud.server:mycloud /mnt/mycloud # glusterfs way = wrong # mount -f ~/mycloud-fuse.vol /mnt/mycloud # cloudfs way = right
At this point, you have a remotely accessible directory with encrypted communication, but data on the remote server that’s still accessible to anyone who can get into that server. In other words, you’ll have something practically equivalent to most of the cloud-storage offerings out there – including the ones you pay for. What you need, both to preserve your privacy and to comply with many companies’ information security policies (such as Red Hat’s), is pure client-side encryption. That’s where CloudFS comes in . . . or at least part of it. At this point, you need to be a bit of a coder or fairly advanced sysadmin, because I’m going to make you pull the code and build your own RPM. I’ll provide some RPMs shortly; also, note that you specifically want the “aes” branch for now. To make it work for you, you’ll need to edit that client-side volfile again, adding a new “encryption/crypt” stanza at the end like this:
volume mycloud-crypt type encryption/crypt option key %0123456789abcdef0123456789abcdef subvolumes mycloud-client-0 end-volume
The key can be whatever you want, at 128/192/256 bits, and can also be stored in a file (use a first character of “/” instead of “%” in the volfile). One easy way to generate such a key is like this:
dd if=/dev/urandom bs=16 count=1 | od -tx1 -An | tr -d '\n '
In any case, the resulting volfile contains nothing but the two stanzas I’ve shown, in that order. All of the “performance” translators which can interfere with proper operation of the encryption code need to be stripped out.
At this point you should be able to mount using your custom volfile to have full encryption both on the network and on disk, with all of the keys safely on your own client system(s). Performance might not be all that great for some kinds of operations, but I’m using it myself and it seems adequate for most purposes. Some day I’ll finish the UID-mapping translator so that you can use this from different UIDs on different machines without getting permission errors, and I’ll finish the built-in SSL transport so you can connect directly instead of needing an ssh tunnel. Then it’ll be really cool, but you know what might be even cooler? With GlusterFS 3.2 you could even replicate this data across two different cloud providers, giving you all of that “multi cloud” goodness that has been all the rage since the EBS outage. With CloudFS 1.0 you’ll be able to do it an even better way, with better consistency and decent performance and so on. At that point I’ll seriously start to question the sanity of anyone who’s using some other solution that doesn’t offer the same performance and the same levels of data protection from both accident and intrusion, or which isn’t open-source like everything I’ve talked about.
For a long time now, I’ve been running a server in the Rackspace cloud to do various things for me, including a sort of Dropbox equivalent to which I sync various files I want to be accessible from everywhere. Historically this has involved a combination of sshfs and encfs, but it’s about time I started eating my own dog food and using (some parts of) CloudFS for this. Yes, I know some people don’t like the “dog food” terminology, but the oft-cited “drinking our own champagne” alternative is even less applicable in this case. I wrote it. It’s still dog food until I say otherwise. Even as I write this, I’m copying files from the old setup to the new one based on pretty vanilla GlusterFS plus the at-rest encryption translator from CloudFS, all mounted on my desktop at work. I’ll have to run that through an ssh tunnel for now – until I finish writing the SSL translator – to deal with authentication and in-flight encryption issues. Similarly, I need to finish the ID-mapping translator before I could recommend this for use by more than one person per machine. With those caveats, though, I’d still say that the result is usable and secure enough for my own purposes (including compliance with Red Hat’s infosec policies). If anybody else is interested in getting on the “personal CloudFS” bandwagon, I’ll post some detailed instructions on how you can do this yourself.
Extended attributes are one of the best kept secrets in modern filesystems. Here you have a fully general feature to attach additional information to files, supported by most modern filesystems, and yet hardly anybody seems to use it. As it turns out, though, GlusterFS uses extended attributes – xattrs – quite extensively to do almost all of the things that it does from replication to distribution to striping. Because they’re such a key part of how GlusterFS works, and yet so little understood outside of that context, xattrs have become the subject of quite a few questions which I’ll try to answer. First, though, let’s just review what you can do with xattrs. At the most basic level, an xattr consists of a string-valued key and a string or binary value – usually on the order of a few bytes up to a few dozen. There are operations to get/set xattrs, and to list them. This alone is sufficient to support all sorts of functionality. For example, SELinux security contexts and POSIX ACLs are both stored as xattrs, with the underlying filesystems not needing to know anything about their interpretation. In fact, I was just dealing with some issues around these kinds of xattrs today . . . but that’s a story for another time.
The sneaky bit here is that the act of getting or setting xattrs on a file can trigger any kind of action at the server where it lives, with the potential to pass information both in (via setxattr) and out (via getxattr). That amounts to a form of RPC which components at any level in the system can use without requiring special support from any of the other components in between, and this trick is used extensively throughout GlusterFS. For example, the rebalancing code uses a magic xattr call to trigger recalculation of the “layouts” that determine which files get placed on which servers (more about this in a minute). The “quick-read” translator uses a magic xattr call to simulate an open/read/close sequence – saving two out of three round trips for small files. There are several others, but I’m going to concentrate on just two: the trusted.glusterfs.dht xattr used by the DHT (distribution) translator, and the trusted.afr.* xattrs used by the AFR (replication) translator.
The way that DHT works is via consistent hashing, in which file names are hashed and the hashes looked up in a table where each range of hashes is assigned exactly one “brick” (volume on some server). This assignment is done on each directory when it’s created. Directories must exist on all bricks, with each copy having a distinct trusted.glusterfs.dht xattr describing what range of hash values it’s responsible for. This xattr contains the following (all 32-bit values):
- The count of ranges assigned to the brick (for this directory). This is always one currently, and other values simply won’t work.
- A format designator for the following ranges. Currently zero, but this time it’s not even checked so it doesn’t matter.
- For each range, a starting and ending hash value. Note that there’s no way in this scheme to specify a zero-length range, nor can ranges “wrap around” from 0xffffffff to 0.
When a directory is looked up, therefore, all the code needs to do is collect these xattrs and combine the ranges they contain into a table. There’s also code to look for gaps and overlaps, which seem to have been quite a problem lately. It doesn’t take long to see that there are some serious scalability issues with this approach, such as the requirement for directories to exist on every brick or the need to recalculate xattrs on every brick whenever new bricks are added or removed. I have to address these issues, but for now the scheme works pretty well.
The most complicated usage of xattrs is not in DHT but in AFR. Here, the key is the trusted.afr.* xattrs, where the * can be the name of any brick in the replica set other than the one where the xattr appears. Huh? Well, let’s say you have an AFR volume consisting of subvolumes test1-client-0 (on server0) and test1-client-1 (on server1). A file on test1-client-0 might therefore have an xattr called trusted.afr.test1-client-1. The reason for this is that the purpose of AFR is to recover from failures. Therefore, the state of an operation can’t just be recorded in the same place where a failure can wipe out both the operation and the record of it. Instead, operations are done one place and recorded everywhere else. (Yes, this is wasteful when there are more than two replicas; that’s another thing I plan to address some day). The way this information is stored is as “pending operation counts” with xattrs recording counts (each 32-bit) for three different kinds of operations:
- Data operations – mostly writes but also e.g. truncates
- Metadata operations – e.g. chmod/chown/chgrp, and xattrs (yes, this gets recursive)
- Namespace operations – create, delete, rename, etc.
Whenever a modifcation is made to the filesystem, the counters are updated everywhere first. In fact, GlusterFS defines a few extra xattr operations (e.g. atomic increments) just to support AFR. Once all of the counters have been incremented, the actual operation is sent to all replicas. As each node completes the operation, the counters everywhere else are decremented once more. Ultimately, all of the counters should go back to zero. If a node X crashes in the middle, or is unavailable to begin with, then every other replica’s counter for X will remain non-zero. This state can easily be recognized the next time the counters are fetched and compared – experienced GlusterFS users probably know that a stat() call will do this. The exact relationships between all of the counters will usually indicate which brick is out of date, so that “self-heal” can go in the right direction. The most fearsome case, it should be apparent, is when the xattrs for the same file/directory on two bricks have non-zero counters for each other. This is the infamous “split brain” case, which can be difficult or even impossible for the system to resolve automatically.
Those are the two most visible uses of xattrs in GlusterFS but, as I said before, there are others. For example, trusted.gfid is a sort of generation number used to detect duplication of inode numbers (because DHT’s local-to-global mapping function is prone to such duplication whenever the server set changes). My personal favorite is trusted.glusterfs.test which appears (with the value “working”) in the root directory of every brick. This is used as a “probe” to determine whether xattrs are supported, but then never cleaned up even after the probe has yielded its result. The result of all this xattr use and abuse is, of course, a confusing plethora of xattrs attached to everything in a GlusterFS volume. That’s why it’s so important when saving/restoring to use a method that handles xattrs properly. Hopefully, I’ve managed to show how crucial these little “extra” bits of information are and perhaps given people some ideas for how to spot or fix problems related to their use.