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  1. #1

    Arrow RAID1 Newbie Question {Help}

    Until now we were using 2 SATA drives on each server and taking backup on secondary drive. In case of server crash, we have software that rebuilds server and everything is back operational in 2-5 hours depending on number of sites.

    Now, we are going to take a Dual Xeon 3.0 1GB RAM 160 SATA server with hardwre RAID1. This is a DELL server. While searching WHT I noticed people saying that RAID failed and both drives were corrupt leaving no backup behind. My qustion is:

    1. Should we go for RAID1 or the current manual backup solution would be more safe forus.
    2. If we go with RAID shall we take additional offsite backups?

    What are Pros and Cons of RAID1 vs manual backup and rebuild.


  2. #2
    Where did you read that raid1 fails and corrupts both drives??

    I think that's probably some sort of crappy software raid ...

  3. #3
    Quote Originally Posted by papi
    Where did you read that raid1 fails and corrupts both drives??

    I think that's probably some sort of crappy software raid ...
    here
    http://www.webhostingtalk.com/showth...ghlight=RAID+1

  4. #4
    Join Date
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    Software RAID is really not all that bad....

    Hostbreak - yes it is completely possible that the entire array can go down at once. RAID is nice and helps prevent data loss but it is not that hard to loose everything all at once. Think about this both of your drives are connect to the same power supply, the same controller card, and same system board. If you have some sort of power problem or hardware failure it could cascade and cause you trouble.

    It is also possible that the array itself can just become corrupt, we have had issues with this in the past and the CLI tools were not able to rebuild it leaving us with a dead array.


    You should NEVER rely on RAID as your only form of backup, make some remote backups
    John W, CISSP, C|EH
    MS Information Security and Assurance
    ITEagleEye.com - Server Administration and Security
    Yawig.com - Managed VPS and Dedicated Servers with VIP Service

  5. #5
    Join Date
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    RAID1 is a good solution to increase availibility somewhat, since the risk of system crash due to hard drive failure is lower. But it is not an excuse to not take regular backups! There is still a lot that can go wrong that might require a restore from another source, including hardware failure, user screwups and software bugs. So your #2 is the correct thing here, go for raid1 but keep another backup as well.
    We do co-location and system management in Stockholm, Sweden. Unfortunately we cannot host you, but i'm sure you'll be ok.

    Remember, the best backup in the world is the one you make yourself.

  6. #6
    In our 4 years history we faced hard disk crash only once. All the times it was Windows that got corrupt. So, with RAID1 when OS gets down to its knees it will happen on both drives, YES?

    Thanks.

  7. #7
    Join Date
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    Yes, raid 1 will not protect you from software failure. If windows dies due to a bad driver or whatever, it wont matter if that driver's files are securely stored
    We do co-location and system management in Stockholm, Sweden. Unfortunately we cannot host you, but i'm sure you'll be ok.

    Remember, the best backup in the world is the one you make yourself.

  8. #8
    For Windows servers Acronis makes a great imaging product, Acronis TrueImage Enterprise. You can backup your server to an image file, boot from a floppy with network support, and reload the image within an hour tops.

  9. #9
    Join Date
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    RAID doesn't protect from file system corruption either, just the failure of a hard drive. Hardware RAID is obviously the better solution because the RAID array can be rebult before booting into the OS

  10. #10
    I have got all answers. Thanks everyone

  11. #11
    Join Date
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    FYI - If you are using SATA raid, please make absolutely certain both the raid controller and the individual drives have their write caching disabled. In recent months I have seen way too many corrupted raids due to drive caching being left on.
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

  12. #12
    Join Date
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    Quote Originally Posted by trau
    FYI - If you are using SATA raid, please make absolutely certain both the raid controller and the individual drives have their write caching disabled. In recent months I have seen way too many corrupted raids due to drive caching being left on.
    Is this the same for any type of drive on a RAID like IDE and SCSI?

  13. #13
    Join Date
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    Yes and no. Write caching is alway potentially dangerous, however the only raid controllers I've run across that by default leave drive caching enabled have been SATA. The SCSI and SAS raid controllers I've used alway disable the drives cache and use only the controllers cache (which defaults to write-thru) to avoid problems (although there may be models that don't). I can't tell you about IDE raid, never used it on a server.
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

  14. #14
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    I use Raid 1 but also have a backup system separated from you for double protection, raid 1 is more for hardware redundancy

  15. #15
    Join Date
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    Quote Originally Posted by boonchuan
    I use Raid 1 but also have a backup system separated from you for double protection, raid 1 is more for hardware redundancy
    Absolutely, RAID should never be used in place of a regular backup. RAID (1+) will only protect you from a hard drive failure, it will not protect you from all the other ways data can be lost/corrupted.
    For most of my clients their business servers use either RAID5 or RAID6(ADG) with hotspares, Livestate images on NAS (also using raid), and tape for offsite and archiving.
    "Arms discourage and keep the invader and plunderer in awe, and preserve order in the world as well as property... Horrid mischief would ensue were the law-abiding deprived of the use of them." - Thomas Paine

  16. #16
    How do you disable write caching on:

    Centos 4.2
    Western Digital Raptor drives
    3ware 8006-2LP sata raid controller

    Any ideas?

  17. #17
    Join Date
    Jul 2003
    Posts
    75
    I am interested in this too... Does anyone know how to disable write cache?

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