advice to configure snapRaid

  • Hello,
    Sorry for my poor english :S
    I am a beginner with snapraid. i read some thread and documentation about snapraid but i still ask myself what is the better way to configure it.
    i explain:
    I have
    HD1 sda 2To
    HD2 sdb1 1To
    HD2 sdb2 1To
    HD3 sdc1 500Go
    HD3 sdc2 2,5to

    today, datas are on HD1 , HD2 and the sdc1 partiction of HD3 (500Go )

    for you, what are the best ways to configure snapraid to "backup" all datas ? the way to avoid the maximum loss ?

    Thank you all and best wishes for the festive season

  • Adding drives to SNAPRAID is straight forward.

    Install the plugin.

    In the Drives TAB, add your drives. (The prerequisites are that drives are formatted and mounted.)

    - As you add drives, note that at least two drives MUST have a content file. Without at least one good copy of the content file, recovery is not possible. (It would be best to set content files on two of the larger drives.)
    - The parity drive must be the largest drive. (This is required for the parity calculation. In your case that would be the 2.5TB drive.)


    In scheduled tasks, I would automate a SYNC job to make sure it gets done. In the following the job kicks off at 01:00AM every Sunday. (Since a sync job will take some system resources, this is best done after-hours.)


  • hello,
    thanks for your answer. one other question please ;)
    when you said "largest drive", do you mean "largest partition" ?
    because my largest partition is 2,5To, but it is on a 3To drive :)
    thanks a lot and happy new year

  • No, I meant the largest physical drive. While I haven't tried it, I'm guessing you can split drives up into block devices using partitions, but this would add complexity to a restore and it could mean the loss of data.

    For the parity drive, partitioning doesn't make sense.
    If the parity drive is used exclusively for parity, and the parity drive dies, this is not a problem because it contains no data. Simply replace the parity drive and run a SYNC.
    But if the parity drive is partitioned, the loss of the parity drive also means the ability to restore is lost. This means the second partition on the parity drive is unprotected, and is lost.

    For data drives, if you split drives into two partitions, the failure of a single physical drive means the loss of two block devices. A single parity drive can protect the loss of one block device, so the loss of a physical drive with two partitions would mean the loss of two logical drives. In that scenario the physical drive can't be recovered, without two parity drives.

    In the bottom line, I believe you could set up logical partitions but you'd need to give thought to failure modes and how to recover. If you divide drives up into block devices, recovery complexity goes up. Also, multiple block device failures would require multiple parity drives to recover.

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