ZFS and SMR drives: To Raid or not to Raid, that is my question.

StephenCND

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Dec 21, 2021
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I've decided to put together a NAS from spare parts I have accumulated over the years. It will be used principally as a media server for occasional use and a place to back up some files. It will not be on 24/7 or see heavy use. I've made the install of TrueNAS ver. 12.0-U6.1 and all is well so for. The problem is, I purchased 6x 4TB WD Reds and only discovered after the fact that there are serious issues with SRM drives and the ZFS file system. They (SRM drives) are not recommended due to fact they are more prone to failure, in particular due to the long period of time it takes to resilver a drive in the event of a disc failure.
The question I am asking myself is, even if I try to mitigate the DM-SMR issues with ZFS, (Disable TRIM, smaller VDEVs, larger data block sizes, etc..) should I just rather totally avoid raid arrays completely? Or, move on to some other NAS OS that does not use ZFS?
Right now, I'd hate to drop Truenas as I really like it's flexibility and potential to serve my needs.
Right now, I'm leaning towards two options, or a combination of both.
I have 6 WD 4TB SMR drives and 2 WD (Black) 2TB (CMR) drives. (The installed OS & swap files are sitting on a 64GB Kingston SSD). I was thinking of mirroring the two 2TB WD black drives for the documents and backups, and storing all the media on the remaining 6 WD 4TB Red (SRM) drives as a JABODs.
Alternatively, I could place 4 of those WD Red SMRs as a raid Z2 (which I have already done, but haven't transferred any data to them yet), and mirror the 2 remaining WD 2TB SRM's . I'd mirror or JABOD the remaining 2 WD 2TB Blacks.
I guess I am trying to get a sense of how much of an issue or risk it would be if i did any raid arrays.
Again, the Nas it will not be running 24/7 and will see occasional use. Nobody else will be relying on this Nas. The important stuff (documents and some photos) will be backed up elsewhere as well, and will not be stored uniquely on the Nas. Most of the storage will be taken up by media files, and while I would hate to loose them if something went belly up, it would not be the end of the world.
Your opinion/advise on how to set up the storage would be great.
Thanks in advance.
 

sretalla

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move on to some other NAS OS that does not use ZFS?
Recommended if you're going to insist on using SMR.

should I just rather totally avoid raid arrays completely?
If you insist for some reason on using ZFS and SMR disks contrary to all good advice, that (avoiding RAIDZ VDEVs... perhaps using mirrors instead) may be the best way to attempt to avoid the pitfalls of SMR... but you won't be able to escape the nature of ZFS transaction grouping, which is inherently problematic for the way that SMR does its thing, so any period of heavy write operation will be expected to produce potential issues.

Fairly warned... don't do it.
 

StephenCND

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Dec 21, 2021
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Thanks Sretalla for the advise. Bit of a bummer however as i was keen on giving Truenas a try .
I'll be looking around for alternatives then.
 
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