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  1. #1
    sdawg Guest
    How often do RAID arrays break? Is it worth having RAID if a servers hard drive goes down? I was thinking it may just be a better option to just have a backup drive mounted to my system and in the even of a system failure just pop in a new hard drive, reload the OS, and then reload all my backups? Bad idea or?

  2. #2
    RAID is not a replacement for backups which you should have off server anyway.

  3. #3
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    sdawg, i've questioned this myself. We use raid1 (software raid) on our linux servers and in talking with our noc techs I asked if it was possible to remove the raid on a server that was deployed with it. I was told by them that you couldn't but google seems to tell me otherwise. If the noc techs we have are right then it would seem like the failure of one drive would be a problem.
    According to Wikipedia raid1 is good though, im not sure if they are referencing software or hardware raid, i'd probably put more confidence in hardware raid.

  4. #4
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    RAID of any level is not a backup solution. Off server backup is always recommended. How often do they break? Once would be too often for me.

  5. #5
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    RAID1 should be a minimum of any server. Use RAID and backups.
    Linux software RAID-1 is very good

  6. #6
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    How often do RAID arrays break?
    I've had drives fall out the array but the monitoring software notifies you and you pop them back in, or in that case upgrade the firmware to resolve a known bug with the drive then add it back into the array.
    I have one raid card fail on me, once in something like 12 years.
    Otherwise it's only if a drive actually fails.
    Is it worth having RAID if a servers hard drive goes down? I was thinking it may just be a better option to just have a backup drive mounted to my system and in the even of a system failure just pop in a new hard drive, reload the OS, and then reload all my backups? Bad idea or?
    It takes seconds or minutes to swap a failed drive and then the server is online and rebuilding the array while serving client data. Doing an OS reload and restore can take hours, also you've lost all the data since the last backup RAID should stop any data loss.
    As stated above you must continue to do offsite backups because RAID doesn't replace backups at all it just reduces downtime.

  7. #7
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    As others have mentioned, RAID is not a backup solution.
    That said, RAID does help to reduce the likelihood of downtime (and potentially data loss) in the event of a hard drive failure.
    -mike

  8. #8
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    Provided that you use a proper RAID-1 set up, you should be fine, but you should maintain backups anyway, you're never too safe.
    RAID-1 also has performance benefits versus a single drive. You're also going to increase load if you backup to a "backup drive".

  9. #9
    mysteryisdiman Guest
    Raid 1 whether it be Software of Hardware is not a bad option especially when I have ran across customers who has Cpanel and has a backup drive and some how their main drive dies and when you check /backup what do you know its empty. Having a little redundancy goes a long way like tolra said its easier to do a rebuild than a reload. Customers hate downtime.

  10. #10
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    Provided that you use a proper RAID-1 set up, you should be fine, but you should maintain backups anyway, you're never too safe.
    The main advantage of backups is being able to go back in time. Raid w/ redundancy just reduces the likelihood the server will go under if a drive fails. If your site gets hacked or you accidentally delete half your root partition, raid will provide no protection.
    RAID-1 also has performance benefits versus a single drive. You're also going to increase load if you backup to a "backup drive".
    This is the #1 reason I would use raid, it increases performance. Especially considering when the hard disk is the slowest part of the server. The more you reduce that bottleneck the happier the server (and you) will be.

  11. #11
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    I use Linux software RAID-1 and RAID-5 on some servers but have off-site back-ups for all servers.

  12. #12
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    sdawg, i've questioned this myself. We use raid1 (software raid) on our linux servers and in talking with our noc techs I asked if it was possible to remove the raid on a server that was deployed with it. I was told by them that you couldn't but google seems to tell me otherwise. If the noc techs we have are right then it would seem like the failure of one drive would be a problem.
    According to Wikipedia raid1 is good though, im not sure if they are referencing software or hardware raid, i'd probably put more confidence in hardware raid.
    In theory you should be able to reconfigure your server so that it is no longer a RAID system. In reality, it takes so much work (at least more than most datacenters are willing to do) that it is much easier to just move your data to a new server. If you have hardware RAID then it is really difficult since for most (if not all) hardware cards, turning off RAID is a destructive process (i.e., nuke all of your data and start from scratch). Software RAID is similar, and requires some skill to safely remove the RAID configuration from your drives. Since most datacenters see that as a decrease in redundancy and reliability, most do not even bother to set up any procedures for that process (other than offer to move your data to a new server).
    If you have a failure of a single drive in a RAID1 array (either software or hardware) then it is not a problem since all you would have to do would be to put a new drive in and tell the controller (or the software drivers) to rebuild the array. That's not considered "removing RAID", it is "replacing a failed member of an existing RAID array", and it happens all the time.
    The important question you should be asking is whether or not your server's chassis is using hot-swappable drives. If it isn't, then it will require downtime to replace the hardware. If it is, then you and your customers may never even notice when you have had a drive fail and replaced in your server.

  13. #13
    No server where you should be storing any customers data on should be anything less then RAID-1. If it is, you are cheating your clients out of their money unless you are charging them like $2's per year. Hard drives have moving parts, and they wear out, they fail. It's bound to happen eventually. Do not worry about a RAID card failing... if it happens, well it happens, but it surely doesn't happen often and I am guessing you will have multiple hard drive failures before running into a HARDWARE raid failure.
    If it is your own server, be my guess.. do not use raid if your budget doesn't allow it, however be sure to take a offsite backup often as that single drive is going to fail you soon rather then latter.

  14. #14
    The best setup will be to have RAID 1 with OS and data on it and then 3-rd drive with a backup. If it too expensive, and short downtime is acceptable, then your solution is better then to have RAID1 (what if by mistake some files will get deleted - no backup - problems).

  15. #15
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    The best setup will be to have RAID 1 with OS and data on it and then 3-rd drive with a backup. If it too expensive, and short downtime is acceptable, then your solution is better then to have RAID1 (what if by mistake some files will get deleted - no backup - problems).
    It is better to have backups off the physical server. Even though the chances are pretty slim it is still possible that the entire box will go at once. Offsite backups are pretty easy to implement, there are several solution providers in the market and tools like duplicity can make encrypted backups to s3 a snap.

  16. #16
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    especially if the server dies during a backup or restore process, and damages the 3rd drive's partition/meta information causing even more distress.
    Or if the server is down for extended time, you cannot access your backup data (to move to another server, provider or a temporary mirror) until the server is back up, so it is kind of pointless :-)

  17. #17
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    Is it worth having RAID if a servers hard drive goes down?
    Yes; RAID can allow continued operation till the drive is replaced.
    That's probably the main use of RAID.

  18. #18
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    We've had 2 RAID cards fail and corrupt their drives in about 8 yrs. It's pretty rare. In one of those cases we later realized the datacenter had skimped on the BBU (battery backup unit) for the RAID controller.
    We've had a couple drives fail the proper way in RAID-1/RAID-10 and it's painless to hotswap the drive.
    The RAID gives you a buffer to swap drives without powering down; but as everyone else has said, it's crucial to have good enough backups to recover your important data even if the box were to disappear from the Internet entirely. Without a RAID-1 you can still recover just fine from good backups, but you're building in mandatory downtime. That doesn't usually make customers very happy.

  19. #19
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    RAID 1 does not provide any performance benefits, in fact it actually hinders the performance of the drives since it is accessing both for read/write.
    That being said, it is still a great idea to have RAID 1, preferably hardware, in just about any server environment situation.
    /2cents
    ~Ryan

  20. #20
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    Of course it's better to have some level of RAID rather than none at all. Best to have RAID and remote backup.

  21. #21
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    RAID 1 does not provide any performance benefits, in fact it actually hinders the performance of the drives since it is accessing both for read/write.
    That being said, it is still a great idea to have RAID 1, preferably hardware, in just about any server environment situation.
    /2cents
    ~Ryan
    The performance for read increases because it can access either drive for the same information.

  22. #22
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    The performance for read increases because it can access either drive for the same information.
    Ah yes, good point
    I was mistaken.

  23. #23
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    Ah yes, good point
    I was mistaken.
    A *GOOD* RAID1 card splits reads by reading half the read from one disk and one from the other.. thus read speed is increased a bit (not 2x a disk, but a good increase), whereas writes are always at the speed of the slowest disk in the RAID1 since it must write to all disks.
    As of this posting, however, I'm pretty sure the Linux MD software raid driver still doesn't split reads amongst the heads, so there's little performance benefit to software RAID 1 on Linux. I believe the same is also true of Windows, but I'm less sure of that one.
    The same is true of any number of lower-end and even a few higher-end RAID cards.. be careful when buying a RAID card that it actually does split reads between heads in a RAID1 if that's a feature you want/need!

  24. #24
    I only use and recommend RAID 10. I have seen both drives fail at the same time in raid 1. It is actually quite common if the drives are from the same supplier made at the same time.
    Harddrives will fail, its just a question of when. I would always use a raid 10 setup if you have enough drive bays.

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