Hey there,

 

I've been using Unraid since years (updated to 7.0 today), new disks were added and right now I've got 2 parity disks (16TB, future proof) as well as 11 array disks with 4/6/8 TB totaling 70 TB. The Unraid server is not 24/7, I just start it a few times a week for some hours. All disks are encrypted (call me paranoid if you like...)

 

The really important files are synced to a second Unraid server which is off until a sync is triggered manually, so no need to discuss the topic of backups, I am aware of that.

 

I want to address the risk of bitrot (which Unraids parity disks do not help with): BTRFS and ZFS are the options. What I found out so far when it comes to bitrot... please correct me if I am wrong:

• ZFS requires 2-n disks of same size, n has to be specified from the beginning and cannot be changed later, ECC and lots of memory must be used (I'd call this "enterprise" league)
• BTRFS requires 2-n disks of different size, disks can be added later (I'd call this "prosumer" league), memory friendly

 

ZFS:

I could set up multiple pools, adding disks of same size to each pool and use RAIDz1. I'd be loosing one disk for data in each pool (and I would need more memory or set up cache disks).

 

BTRFS:

I used the "btrfs disk usage calculator" (details in the link) - RAID5, resulting in 62 TB being available and 8 TB used for parity. So one disk could die and I'd still be able to recover the whole data, and bitrot on any file on any disk is correctable. All these disks would be added to one "pool" so that the OS sees them as a "bunch of disks". But of what use are the dual parity disks in Unraid if I'd go to RAID6 then, apart from the disk being emulated as being present, which is no biggie as I can wait for replacements?

 

I guess for my scenario, it would make sense to convert one disk after another to a BTRFS "pool" I assume (move files to external disk, add to pool, format BTRFS, copy files back, repeat)?

 

Thanks for your thoughts!

Don't recommend using btrfs raid5/6, it's still considered experimental, recommend using zfs raidz instead, starting with Unraid 7.1, it will be possible to expand a raidz pool, though possibly only using the CLI initially, but it's easy to do, of course raidz is still not as flexible as btrfs raid5, but like mentioned I would not recommend using that for production, maybe if you have very good backups.

15 hours ago, MichaelAnders said:

ECC and lots of memory must be used (I'd call this "enterprise" league)

P.S. This is not correct, while I would recommend using ECC with btrfs and zfs, it's never required, but it's good to have, especially if you are concerned with data integrity, regarding RAM, for media or any other WORM data you don't need a lot of RAM, 8GB would be more than enough.