2 Parity + 1 Data Disk

[landS]

Strange question for you goodly folks. 

Is there any benefit to using 2 Parity Disks with 1 Data Disk?

 

My array is comprised of 5 data disks and 2 parity drives - all 4 TB with an average power on time of around 7 years.

I am replacing these with 3 20 TB disks:  2 Seagate IronWolf Pro CMR & 1 WD Red Pro CMR

 

If no benefit to using 2 Parity Disks with 1 Data Disk, I will keep 1 of the disks as a pre-cleared hot-spare. 

 

Thanks!

 

[itimpi]

I would definitely not bother with 2 parity disks with 1 data drive.   Even with the 5 data drives you currently have 2 parity disks feels like a bit of overkill.

 

Another option to consider is to run without any parity disks and then leave one of the 20TB disks to do regular backups while keeping the other as a hot spare.   This way you have two independent copies of your data.

 

If you move to 2 data drives then I would consider 1 parity drive more than enough.

 

You should always have backups of of any important or irreplaceable data as there are other ways to lose data than a disk failing (which is what parity protects you against).

 

[landS]

Thanks itimpi!

 

I rather like the option for disk fault tolerance, and also think the backup is a good idea.  I'll stick to 1 parity and 1 pre-cleared spare. 

 

I have a second unraid server with no exported network shares that I turn on quarterly and run 2 backup scripts:

• For write once, never change: rsync -r -v --progress --ignore-existing -s /mnt/disks/TOWER_WriteOnce/WriteOnce/ /mnt/user/Media/WriteOnce
• For write many: rsync -av --progress --delete-before /mnt/disks/TOWER_WriteMany/WriteMany /mnt/user/WriteMany

 

In addition, I run the Crashplan Docker on folders containing important data.