Newb question: HD upgrade with imbalanced vdev's

[N123]

Hello all,

Newbie/new-to-TrueNas user here.

I am running the latest version of TrueNas core on an old server with 3 bays available for data storage. Currently I have 2 of these bays occupied with 2x4TB WD Red Drives setup in a mirror configuration with the 3rd bay in the server empty.

I have already used up 80% of my HD space in the above configuration and am looking to upgrade my available storage space by adding a HD to the currently empty 3rd HD bay in my server--my two options are (1) another 4TB WD red drive or (2) 12tb shucked WD white label drive as I already own these and want to avoid sinking more $$ into this endeavor.

What do you recommend to expand space for data storage?

Ideally, I would like to have the 12TB white label WD in bay 3 as a mirror for 4TB+4TB=8TB for what is currently in bay 1 and bay 2 (thus allowing the server to have a total of 8TB of useable space since the data would be mirrored). . . is this possible or is there is a better config you recommend? . . . if needed I can destroy the data already on the TrueNAS and recopy it over from another device but it would be nice to avoid this if possible for the upgrade

Thanks,
N123

 

[N123]

 

[N123]

It looks like my best option is to tear everything down and then set a Raid Z-1 setup with the 3 WDRed4TB drives?--this will expand my storage capacity but still allow for some parity. Unless someone chimes in with a way to keep my existing data on the server or if it's possible to do my preferred setup 2xWDRed4TB=8TB (combined in a single data set) and then mirror the data to my 12 White label WD...

 

[N123]

Can someone point me to another thread/reference that answers my question for the above scenario? I believe the most efficient option (assuming I can't mirror my 12 tb white WD drive to a 4+4=8tb [composed of two 4tb WD red drives] to allow a total of 8 TB mirrored data) will be erase all the data currently stored on my TrueNas and start over w 3 x 4tb WD red drives in a Raid Z-1 setup (I don't believe I can "add" a 3rd 4tb WD drive to my already-running mirrored 4tb mirror setup). Thanks

 

[ChrisRJ]

Not sure this matches your requirements, but not too long ago there was a thread about converting a mirror to RAIDZ1.

 

[sretalla]

So there are a few things to confirm and to advise here...

You can't (as you said correctly) "convert" the VDEV type from anything to any kind of RAIDZ (that includes going from RAIDZ1 to RAIDZ2, but also can't be from Mirror nor from stripe to RAIDZ1). (just to mention, you can go from Mirror to stripe and single-disk stripe to Mirror, although it's not what you're asking about here).

Members of any VDEV can only be single disks (if you're using the GUI), so your proposal to stripe 2x4TB together and then mirror that to 1x12TB isn't possible using the GUI (and I don't think anyone here will recommend that you do it at all, even if it is "possible" with the CLI via geom and zpool commands) and would make support for that situation quite difficult as it's super-rare for anyone to decide to do it (and those folks usually know what they are doing already, so don't come here asking for help, hence little/no documentation to be found for it).

With a 12TB drive, there would be no good answer (other than a mirror, 2 or 3 way) in terms of only 3 disks, since the guidance for safe operation is that RAIDZ1 should only be used for drives under 2TB due to the extremely long resilver times and the stress that resilvers put on the remaining drives where you have no redundancy for usually a day or even longer if the pool is nearing full.

You could use a hack to work around the need for a complete backup/restore if you have a 3rd drive and wanted to change your mirror to RAIDZ1 (still not recommended even if you only had a 3rd 4TB disk... but better than if it's 12TB), but creating a degraded RAIDZ1 pool with only 2 of the 3 disks in place, copy from your mirror (with one disk remaining in it) and then move the final disk over to complete the RAIDZ1 when the data is there... I recommend against that strategy unless this is a system where the data isn't important to you.

 

[N123]

So there are a few things to confirm and to advise here...

You can't (as you said correctly) "convert" the VDEV type from anything to any kind of RAIDZ (that includes going from RAIDZ1 to RAIDZ2, but also can't be from Mirror nor from stripe to RAIDZ1). (just to mention, you can go from Mirror to stripe and single-disk stripe to Mirror, although it's not what you're asking about here).

Members of any VDEV can only be single disks (if you're using the GUI), so your proposal to stripe 2x4TB together and then mirror that to 1x12TB isn't possible using the GUI (and I don't think anyone here will recommend that you do it at all, even if it is "possible" with the CLI via geom and zpool commands) and would make support for that situation quite difficult as it's super-rare for anyone to decide to do it (and those folks usually know what they are doing already, so don't come here asking for help, hence little/no documentation to be found for it).

With a 12TB drive, there would be no good answer (other than a mirror, 2 or 3 way) in terms of only 3 disks, since the guidance for safe operation is that RAIDZ1 should only be used for drives under 2TB due to the extremely long resilver times and the stress that resilvers put on the remaining drives where you have no redundancy for usually a day or even longer if the pool is nearing full.

You could use a hack to work around the need for a complete backup/restore if you have a 3rd drive and wanted to change your mirror to RAIDZ1 (still not recommended even if you only had a 3rd 4TB disk... but better than if it's 12TB), but creating a degraded RAIDZ1 pool with only 2 of the 3 disks in place, copy from your mirror (with one disk remaining in it) and then move the final disk over to complete the RAIDZ1 when the data is there... I recommend against that strategy unless this is a system where the data isn't important to you.

Thank you--this is extremely helpful. I really appreciate you taking the time to help me out!

 

[Etorix]

The best option to expand space while keeping data safe is to add the 12 TB drive to the mirror (3-way), buy another large HDD (preferably another 12 TB), remove one 4 TB HDD, add the new HDD to the mirror and finally remove the last 4 TB drive to have a mirror with the two large HDDs.

Because resilvering 10+ TB drives takes a long time, and even if resilvering a mirror is somewhat faster and less stressful than resilvering a raidz, you should ideally get a third 12 TB and permanently run the pool as a 3-way mirror: That would ensure redundancy and data safety even after the loss of one drive. It's not space effective, or cost effective, but it's the safest possible option with only 3 bays.