Expanding a zPool?

[Grimm Spector]

Hello, I currently have a zpool with one vdev made up of four large HDDs setup in RaidZ1. The system has four additional SAS connections that I am not currently using, and what I'd ideally like to do is expand the system by giving it an extra four drives of the same and make it into a RaidZ2. My question is, is this possible, and if so how is the safest way to go about it in FreeNAS? If not, perhaps best alternatives? Thanks!

 

[Mlovelace]

Unfortunately you can not convert a raidz1 to a raidz2. You would have to copy the data off the current pool and re-create it as a raidz2 when you get the 8 HDDs. However, you can extend your current pool with another 4 drive raidz1 vdev.

 

[Chris Moore]

Slideshow explaining VDev, zpool, ZIL and L2ARC
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

Terminology and Abbreviations Primer
https://forums.freenas.org/index.php?threads/terminology-and-abbreviations-primer.28174/

Why not to use RAID-5 or RAIDz1
https://www.zdnet.com/article/why-raid-5-stops-working-in-2009/

 

[Heracles]

Hi Grimm,

As Mlove said, you can not just convert a RaidZ1 to RaidZ2. But there is one thing that you can do and you could consider as a kind of RaidZ1.5 if I can say, it is to add an extra drive as a hot spare.

Doing that, your pool remains a RaidZ1 and has only a single redundant drive. But should a drive fail, FreeNAS will turn to the hot spare and re-silver the pool using it. That will reduce your exposure to a failed drive to the minimum possible and once the re-silver is done, you are back to Healthy and can survive a second HD failure.

Not as strong as RaidZ2, still vulnerable to the failure of 2 drives at once, but should the 2 failures be separated by a long enough period for FreeNAS to re-silver, you will end up more robust than just RaidZ1.

If you can migrate your data out of the pool to destroy it and create a new and real RaidZ2, that would be the best. If that is not possible, a RaidZ1 with a hot spare would be better than RaidZ1 without hot spare and that hot spare you can add without destroying the pool first.

 

[Dan Tudora]

Slideshow explaining VDev, zpool, ZIL and L2ARC
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

Terminology and Abbreviations Primer
https://forums.freenas.org/index.php?threads/terminology-and-abbreviations-primer.28174/

Why not to use RAID-5 or RAIDz1
https://www.zdnet.com/article/why-raid-5-stops-working-in-2009/

hello Chris
can do an exercise of imagination ??

it's a way to do that, is dangerous but can work

put the last 4 SAS drive in system
offline 1 drive from 1'st pool (degraded)
create second RAIDZ2 pool with the 4 new hdd and with 1 from 1'st pool and 1 from USB drive in degraded mode with 2 sparsefile like
https://forums.freenas.org/index.php?resources/creating-a-degraded-pool.100/
use ZFS send/receive to transfer data
replace sparsefile and USB drive after data transfer
what you say, can work ??

 

[Grimm Spector]

hello Chris
can do an exercise of imagination ??

it's a way to do that, is dangerous but can work

put the last 4 SAS drive in system
offline 1 drive from 1'st pool (degraded)
create second RAIDZ2 pool with the 4 new hdd and with 1 from 1'st pool and 1 from USB drive in degraded mode with 2 sparsefile like
https://forums.freenas.org/index.php?resources/creating-a-degraded-pool.100/
use ZFS send/receive to transfer data
replace sparsefile and USB drive after data transfer
what you say, can work ??

I too would love to know the answer to this. Though I'm not sure I'm following on a the USB drive bit.

 

[Heracles]

Hey Grim,

Before Chris gives you his answer, I will just resume the idea exposed by Dan as playing poker with your data. Are you ready to loose everything and have your pool destroyed ? If you are not, then no need to look any further.

The reason is that the procedure involves reducing the protection of your pool down to 0. If anything goes wrong during that procedure, your main pool ay very well ended up ruined and impossible to recover.

Technically, I did something similar with my pool, but downgrading it from RaidZ2 to RaidZ1 for the moment of the procedure. Despite a limited protection, my pool remained protected at all time. Here, because you start from RaidZ1, to reduce your protection put you bare naked and you will not survive an incident during that window.

 

[Dan Tudora]

hello Grim
hello Heracles

first of all Grim if you want help, must to specify your hardware configuration and FN version
with this things must to start
1 have other SATA port free on motherboard
2 your boot drive is on USB/SATA (1 or 2 drive in mirror??)

and Heracles you a right but with more technical specification from Grim can help Grim to make something good and safe with this problem
maybe Grim can buy a 10 TB HDD to backup data and this discussion have not object