mdadm vs snapraid

  • Hi guys


    I'm new to openmediavault, I have been using freenas with an old computer having 3TB in Raid 1, but now got new hardware and decided to move to OMV.


    Regarding storage right now I have 2x WD Red 4Tb and 2x WD Green 3TB. My plan is to use the 4TB drives for my important data (documents, photos, archives projects), so I pretend to have some kind of fallback here, and using the 3TB drives just to store not so important stuff (movies, timemachine backup, etc). I know any kind of Raid is not a backup so I'm also planning to use some cloud backup.


    My question is regarding the data storage disks. Should I go with the default Raid 1 (mirror) used by OMV (MDADM) or with the Snapraid solution? The files shouldn't change over time, so as far as I have read Snapraid could be a good candidate, but does it works good with only 2 disks?

    • Offizieller Beitrag

    So Raid 1 would be a better option? Can you please explain me how it would work with unionfs + snapraid in terms of disks layout?

    From what you have described 2 x Raid 1 would be a waste of the drive capacity you have, if you use UnionFS (MergerFS) plugin along with SnapRaid plugin for starters you'll get more usable disk space, but this does not negate the need for a backup. Some use plugins such as Duplicati, Rsnapshot and Rsync.


    Rather than me trying to explain MergerFS and SnapRaid have a look at this ignore the title, but his explanation help me decide that this is the way I should go from my current Raid 5 set up, he also has a follow on from that for 2017. This site albeit using OMV 2 explains how he used the plugins, the SnapRaid site is here there's a lot of information on there.


    At the end of the day it's what you want to use and what you feel comfortable with, I've tried Freenas, Nas$free (now changed it's name) headless Ubuntu server and now OMV. OMV offers much more and found it easier to use for home use, also search the forum you'll find answers to any questions you may have and solutions to problems others have had.

  • I was reading some more documents and as far I understood right now I have two solutions:


    1) Use Raid 1 for the 2x Red 4TB for important data, and use MergerFS (or similar) for 2x Green 3TB (with content I don't mind to lose), which result in 10TB (4 + 3 +3)


    2) Use SnapRaid with one of the 4TB hard drives serving as parity, and the other 3 for data (1x Red 4TB + 2x Green 3TB), merged with MergerFS?, which also result in 10TB


    Have to decide wish is the best solution, having in consideration that:
    1) WD Greens may not be so reliable and they already have a couple of years (not so many use tho)
    2) I pretend to use the NAS has timemachine backup also, and not sure if SnapRaid is the most suitable for that


    edit: a third solution would be to use a single 3TB drive for timemachine backups, and use SnapRaid on the other (4TB drive for parity, 3 + 4 as data)

    • Offizieller Beitrag

    edit: a third solution would be to use a single 3TB drive for timemachine backups, and use SnapRaid on the other (4TB drive for parity, 3 + 4 as data)

    Well just by looking at what you have available and what your requirements are you have come with three possible solutions, which one is going to be most suitable and how you back these up, including the timemachine backups. But each option you have come up with is doable and you've identified that the WD Greens could be the weak link.

  • Thanks for your help. I decided to go with the third solution for now: 1x 3TB Green only for timemachine (this way I let timemachine that use a lot of small files that change frequently out of snapraid), and I will also have the media downloads protected with snapraid.

    • Offizieller Beitrag

    Actually, you can use SNAPRAID with 2 disks (versus using RAID1). An advantage over RAID1 would be checksummed files, the ability to scrub and fix bitrot, and the restoration of deleted files (depends in the last sync).
    (**2 disk setups are not widely used, or documented, but I've tested it.**)


    If you do this (a 2 disk setup), using the OMV plugin, you'd need a content file on the parity disk. In the event of a data drive failure, without a good content file, there would be no restoration of the data drive.
    ___________________________________________________________


    Thanks for your help. I decided to go with the third solution for now: 1x 3TB Green only for timemachine (this way I let timemachine that use a lot of small files that change frequently out of snapraid)

    I use a single drive (3TB) on OMV, for client backup, using UrBackup. If the bulk of your data storage is on your OMV server, not on clients, 3TB is more than sufficient.

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