ZFS vdev Expansion in zfs 2.3.0

R

recluce

Apparently, the ability to expand a zfs vdev "one drive at a time" is finally going live with zfs 2.3.0, see here zfs 2.3.0rc3 release notes - "RAIDZ expansion"

I do not want to discuss the drawbacks of doing so here, that is well documented in the related commit: zfs commit 15022

I am just wondering if somebody cares to take an educated guess when we might see zfs 2.3.0 and in which FreeBSD versions.
 
FreeBSD-current-15 seems to spin upt toward ZFS 2.4.

So I guess 2.3 might happen in 14.x? 2.3 is a cool release, would like to see it.
 
Pendantic warning :)

I first read this and was confused because as far as I recall a ZFS vdev could be expanded by replacing one device at a time with a larger device. As in "a mirror of 2 1TB devices, replace 1 device with a 2TB device, let it resilver, replace the other with a 2TB device, let it resilver and the mirror is then 2 of 2 TB devices".

But reading the release notes, this sounds like "I have a raidz and I add a new physical device to the raidz".
I don't have anything with raid-z so what are the benefits of allowing this?
 
mer said:
Pendantic warning :)

I first read this and was confused because as far as I recall a ZFS vdev could be expanded by replacing one device at a time with a larger device. As in "a mirror of 2 1TB devices, replace 1 device with a 2TB device, let it resilver, replace the other with a 2TB device, let it resilver and the mirror is then 2 of 2 TB devices".

But reading the release notes, this sounds like "I have a raidz and I add a new physical device to the raidz".
I don't have anything with raid-z so what are the benefits of allowing this?
Click to expand...
The old way requires you to exchange all drives in the vdev before you see any increase in pool size and the new devices have to be larger than the old ones. Adding a single drive to an existing vdev can (should) be done by adding a drive of the same size and will roughly expand pool capacity by the size of the drive once zfs housekeeping is complete. Saves a lot of money in home / SOHO setups.
 
mer said:
But reading the release notes, this sounds like "I have a raidz and I add a new physical device to the raidz".
I don't have anything with raid-z so what are the benefits of allowing this?
Click to expand...

You can expand the usable capacity of the array one disk at a time.

Without having to make a backup, nuking the pool and making a new one.
 
Thanks gents. So the intent is not be to convert say RAID-Z1 to RAID-Z2/3 but to simply add more data space?
 
cracauer@ said:
Yes, you cannot change the raidz level, just the number of disks in the same level.
Click to expand...
Ahh, much like "a mirror is traditionally 2 devices, but one can add a third device to make a 3 way mirror". Yes, I understand adding a device to a mirror does not expand the space (typically a quick way to make a backup) and on the RAIDZ it's just data space and maybe extra device for parity.
 
You must log in or register to reply here.
Back
Top