Comments on: ZFS Administration, Part II- RAIDZ

By: Veniamin

Veniamin — Tue, 30 Apr 2013 06:54:46 +0000

Thanks for articke.
I wonder how RAIDZ will work with two or more parity stripes.
I think that in the case of data is longer than recsize x n_data_disks, raidz slpits it into several writes.

By: Aaron Toponce : ZFS Administration, Appendix A- Visualizing The ZFS Intent LOG (ZIL)

Fri, 19 Apr 2013 11:03:23 +0000

[...] RAIDZ [...]

By: Aaron Toponce : ZFS Administration, Part IX- Copy-on-write

Aaron Toponce : ZFS Administration, Part IX- Copy-on-write — Fri, 19 Apr 2013 10:57:49 +0000

[...] RAIDZ [...]

By: Aaron Toponce

Aaron Toponce — Wed, 27 Mar 2013 19:44:30 +0000

Correct. The image isn’t 100% accurate. I may fix it, but yes. If you lose too much of a single stripe, then you can’t recreate the data. For each stripe written, and this is where my image needs to be updated, a parity bit is written. So, if a stripe crosses the disks twice, then there will be extra parity bits.

Thanks for pointing this out.

By: ssl

ssl — Tue, 26 Mar 2013 17:54:04 +0000

I don’t quite understand how zfs could recover from certain single disk failures in your example (picture) .. say for example you lost the last drive in your raidz-1 configuration as shown. for the long stripe (A) you lose the parity bit as well as the data in block A4… How could this possibly be recovered, unless zfs puts additional parity blocks in for all stripes whose length exceeds the number of disks??

By: Aaron Toponce : ZFS Administration, Part VII- Zpool Properties

Aaron Toponce : ZFS Administration, Part VII- Zpool Properties — Wed, 20 Feb 2013 15:33:45 +0000

[...] RAIDZ [...]

By: Aaron Toponce

Aaron Toponce — Thu, 07 Feb 2013 17:24:28 +0000

No, this is not possible. Other than disks and files, you cannot nest VDEVs. ZFS stripes across RAIDZ and mirror VDEVs, and there’s no way around it. You need to rethink your storage.

By: Alvin

Alvin — Sun, 03 Feb 2013 04:53:11 +0000

Okay here’s one for you, I can’t find ANY documentation ANYWHERE for using brackets (parentheses) to describe what drives to select when creating a zpool. For example, I am in a VERY sticky situation with money and physical drive constraints. I have figured out a method to make the best use of what I have but it results in a pretty unorthodox (yet completely redundant and failproof [1 drive] way) of getting it all to work AND maximize the use of my motherboard’s ports to make it completly expandable in the future. I am basically creating a single-vdev pool containing a bunch of different raid levels, mirrors, and stripes.

HOWEVER, this is how I have to do it, because of hardware constraints.
If you were to imagine how to use the zpool create, this is how it would look USING BRACKETS. BUT THERE IS NO MENTION OF HOW TO USE BRACKETS PROPERLY in any zfs documentation. Basically either brackets, commas, &&s, etc, anything that would give me the desired affect.

zpool create mycoolpool RAIDZ1 ((mirror A B) (mirror C D) (mirror E F) (G) (stripe H, I) (stripe J, K, L) (M))

Yes I have 7 1TB ‘blocks’ or ‘chunks’ in a RAIDZ1, each consisting of different configurations.

You see, if I were to do this without the brackets, it would create this mess:
zpool create mycoolpool RAIDZ1 mirror a b mirror c d mirror e f g h i j k l m
^^Basically you see here that I would end up with a RAIDZ1 across 3 mirrors, the third of which consisting of a redundancy level such that 8 drives could fail… not what I want.

And yes, I have indeed seen all the warnings and read countless people say “you shouldn’t” but NEVER have I seen anyone deny that it could be done and NEVER have I seen anyone actually answer on HOW to do it.

I’ve made up my mind that this is the method and approach that I need to take so please heed your warnings as much as you can as they will be said in vain.

Thank you very much in advance for a response!!!

By: Aaron Toponce : ZFS Administration, Part V- Exporting and Importing zpools

Aaron Toponce : ZFS Administration, Part V- Exporting and Importing zpools — Tue, 08 Jan 2013 04:25:44 +0000

[...] RAIDZ [...]

By: Aaron Toponce : ZFS Administration, Part XI- Compression and Deduplication

Aaron Toponce : ZFS Administration, Part XI- Compression and Deduplication — Tue, 08 Jan 2013 04:23:55 +0000

[...] RAIDZ [...]

By: Aaron Toponce

Aaron Toponce — Sat, 29 Dec 2012 13:24:12 +0000

Fixed. Thanks!

By: boneidol

boneidol — Sat, 29 Dec 2012 02:42:56 +0000

“Instead, in my opinion, you should keep your RAIDZ array at a low power of 2 plus parity. For RAIDZ-1, this is 3, 5 and 9 disks. For RAIDZ-2, this is 4, 8 and 16 disks. For RAIDZ-3, this is 5, 9 and 17 disks”

hi I don’t understand these numbers above

Z1 = 2^1 + 1 , 2 ^2 + 1 , 2^3 +1 = 3,5,9
Z2 = 2^1 + 2 , 2^2 +2 , 2^3 +2 = 4,6,10
Z3 = 2^1 + 3 , 2^2 +3 , 2^3 +3 = 5,7,11

Sorry!

By: boneidol

boneidol — Sat, 29 Dec 2012 02:36:05 +0000

“In relatiy” <- trivial typo

By: Aaron Toponce : ZFS Administration, Part VIII- Zpool Best Practices and Caveats

Aaron Toponce : ZFS Administration, Part VIII- Zpool Best Practices and Caveats — Thu, 20 Dec 2012 15:07:20 +0000

[...] RAIDZ [...]

By: Aaron Toponce : ZFS Administration, Part XII- Snapshots and Clones

Aaron Toponce : ZFS Administration, Part XII- Snapshots and Clones — Thu, 20 Dec 2012 15:06:19 +0000

[...] RAIDZ [...]