FreeNAS zPool adding disk question.

[Devin Acosta]

I am purchasing an HP DL380g8 with 12 drive bays. I want to start off by doing a raidZ2 with 4 drives, then have the ability to add a single drive to the pool for space, not caring about having additional redundancy. Is it possible to create a raidZ2 pool with 4 drives, and just add drives to get space, knowing that I will only be able to loose 2 drives in that pool?

 

[sretalla]

If you add an additional drive, it will be a 2nd VDEV and hence if you lose it your pool is dead.

RAIDZ2 is not expandable at this point, but pool expansion does work, creating a stripe of all VDEVS in the pool with each new VDEV being key for pool survival, so adding a non-redundant VDEV will endanger the entire pool.

You need to go to the reources section and look at the material on ZFS primer information to understand what you want.

 

[Scharbag]

As said, RaidZ2 cannot have additional drives added to an existing vDev. You can add another vDev to the pool. ZFS allows the additional vDev to be whatever you want but best practice is to have matching vDevs.

RaidZ2 with a 4 drive vDev is not a great layout as it is only 50% data efficient. The same efficiency can be had with mirrored vDevs. Another advantage of mirrored vDevs is you can add another mirrored pair at any time. You will always be faced with 50% data efficiency but mirrors are very scalable.

If I could go back in time, I would have configured my RaidZ2 pool with 2 8 drive vDevs instead of 6 drives to get a little better data efficiency while still maintaining adequate fault tolerance as I backup all of my data to a 12 drive RaidZ2 pool. But I digress.

Bottom line, ZFS is not forgiving at all. Plan today for what you will need in 3-5 years, not for what you need today.

Cheers,

 

[GlueFactoryBJJ]

I know I'm late to this conversation, but I have a similar need. When I built my FreeNAS about 18 months ago, I used 6 x 4TB WD RED drives in a RaidZ2 configuration, giving me about 14TB net free space (which is down to about 500GB now, yeah, I know it is killing performance). Fortunately though, my data storage growth rate has slowed a lot now that I have all of my systems backed up. I figure that an additional 8TB (2x4TB RED drives) will cover me for the next couple years. And I'm perfectly happy with the protection of RaidZ2.

So, if I understand what is said in this and other threads, unlike some ancient RAID5 controllers, ZFS still does not allow the addition of drives to an existing vdev unless I backup the data elsewhere and rebuild the vdev with the additional two drives?

I find this frustrating that as good as ZFS is, it still does not support the direct addition of drives to a vdev. I thought I remembered reading (about 12-18 months ago) that the ZFS devs were working on adding this ability. Does anyone know if they are getting close or is this just wishful thinking on my part?

Anyway, if someone can confirm my 1st paragraph and provide some insight on this, IMO, glaring weakness in FreeNAS/ZFS, I'd appreciate it. I'm not a Unix guru, so (re)configuring FreeNAS isn't a simple project for me. It likely will take me the better part of a day to finish the drives addition (in addition to the time necessary to backup and consolidate duplicate storage).

Thanks, in advance, for any help!

 

[GlueFactoryBJJ]

I know I'm late to this conversation, but I have a similar need. When I built my FreeNAS about 18 months ago, I used 6 x 4TB WD RED drives in a RaidZ2 configuration, giving me about 14TB net free space (which is down to about 500GB now, yeah, I know it is killing performance). Fortunately though, my data storage growth rate has slowed a lot now that I have all of my systems backed up. I figure that an additional 8TB (2x4TB RED drives) will cover me for the next couple years. And I'm perfectly happy with the protection of RaidZ2.

So, if I understand what is said in this and other threads, unlike some ancient RAID5 controllers, ZFS still does not allow the addition of drives to an existing vdev unless I backup the data elsewhere and rebuild the vdev with the additional two drives?

Nothing? At least a confirmation?

 

[danb35]

ZFS still does not allow the addition of drives to an existing vdev unless I backup the data elsewhere and rebuild the vdev with the additional two drives?

Correct.

Does anyone know if they are getting close or is this just wishful thinking on my part?

I think there's some status information in this thread:
https://forums.freenas.org/index.php?threads/raidz-expansion-its-happening.58575/