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OpenZFS – add disks to existing RAIDZ

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Re: OpenZFS – add disks to existing RAIDZ

#111
post #3

Wow, I've been hearing this has been in the works for a while. I am glad to see it released! My RAIDZ array awaits new disks!

What do you mean by released? It hasn't even been merged yet. :)

Misread the pull request. But this means it is close to release! It has been in the works for some time.

Re: OpenZFS – add disks to existing RAIDZ

#112
post #30

I wish Apple and Oracle would have just sorted things out and made ZFS the main filesystem for the Mac. Way back in the day when they first designed Time Machine, it was supposed to just be a GUI for ZFS snapshots. How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). I could buy a new external disk, add it to a pool, have seamless storage expansion. It would be great. Ah, what coul…

Yeah I wonder if it was really caused by Jonathan Schwartz bragging to the media about it and pissing Steve Jobs off, as was rumoured at the time. Or if there was more behind it. I would certainly not put it past Jobs. While he had some genius qualities, his personality was pretty deeply flawed. But on the other hand I wonder if his sense for business would not have prevailed. If only Apple had absorbed sun instead o…

Not sure why you limit that to desktop. It's more important that server files can have an instant snapshot, compression and performant incremental backup to remote servers.

Re: OpenZFS – add disks to existing RAIDZ

#113

Earlier quoted context omitted.

> I could buy a new external disk, add it to a pool, have seamless storage expansion. You still can't do that with ZFS though, that's what this PR is for.

You can add devices as vdevs to a pool, though. You can't add disks to a vdev. (IIRC) It's no different to LVM in that aspect.

IIRC, the pool is effectively RAID0 over vdevs: if any single vdev dies - whole pool dies. Do i remember this correctly?

So if over the years I got, say, five disks of varying quality - I shouldn't add them to a pool as five individual vdevs :)

Re: OpenZFS – add disks to existing RAIDZ

#114

Earlier quoted context omitted.

That is not how this will work. The reason the parity ratio stays the same, is that all of the references to the data are by DVA (Data Virtual Address, effectively the LBA within the RAID-Z vdev). So the data will occupy the same amount of space and parity as it did before. All stripes in RAID-Z are dynamic, so if your stripe is 5 wide and your array is 6 wide, the 2nd stripe will start on the last disk and wrap arou…

Could you force a complete rewrite if you wanted to? That would be handy. Without copying all the data elsewhere of course. I don't have another 90TB of spare disks :P Edit: I suppose I could cover this with a shell script needing only the spare space of the largest file. Nice!

> Could you force a complete rewrite if you wanted to?

On btrfs that's a rebalance, and part of how one expands an array (btrfs add + btrs balance)

(Not sure if ZFS has a similar operation, but from my understanding resilvering would not be it)

Not that it matters much though as RAID5 and RAID6 aren't dependable upon, and the array failure modes are weird in practice, so in context of expanding storage it really only matters for RAID0 and RAID10.

https://arstechnica.com/gadgets/2021/09/examining-btrfs-linu...

https://www.unixsheikh.com/articles/battle-testing-zfs-btrfs...

Re: OpenZFS – add disks to existing RAIDZ

#115
post #30

I wish Apple and Oracle would have just sorted things out and made ZFS the main filesystem for the Mac. Way back in the day when they first designed Time Machine, it was supposed to just be a GUI for ZFS snapshots. How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). I could buy a new external disk, add it to a pool, have seamless storage expansion. It would be great. Ah, what coul…

> How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). How cool would it be if we had a great TUI for ZFS... Live in the now: https://github.com/kimono-koans/httm

Now that's a smooth segue to self-promo. I respect it.

Re: OpenZFS – add disks to existing RAIDZ

#116

The big news here seems to be that iXsystems (the company behind FreeNAS/TrueNAS) is sponsoring this work now. This PR supersedes ones that was opened back in 2021 https://github.com/openzfs/zfs/pull/12225#issuecomment-16101...

I hope this corporate sponsorship won't go the way that wireguard went. https://arstechnica.com/gadgets/2021/03/buffer-overruns-lice... What worries me the most is them doubling down on it after it was shown to be a mess and totally insecure. I imagine to protect the corporate image. But such corporate interests don't belong in FreeBSD. Just admit you hired the wrong guy (or the right guy at the wrong time) and take…

iXsystems are an entirely different beast than Netgate (pfSense).

One can trace its legacy to BSD while it was still at Berkley and has worked with many of the most respected names in the BSD space.

The other bought a domain name of a fork and used it to post disparaging messages and Hitler "Downfall" memes slandering them. Source: https://www.wipo.int/amc/en/domains/search/text.jsp?case=D20...

While I have some disagreements with iXsystems' pivot to ZFS-on-Linux offerings and the like, they're not the clowns that Netgate / pfSense are. 10cm to my right are TrueNAS and opnSense boxes - you won't catch me dead using pfSense in my network after the crap they've pulled.

Re: OpenZFS – add disks to existing RAIDZ

#117

Earlier quoted context omitted.

You can add devices as vdevs to a pool, though. You can't add disks to a vdev. (IIRC) It's no different to LVM in that aspect.

IIRC, the pool is effectively RAID0 over vdevs: if any single vdev dies - whole pool dies. Do i remember this correctly? So if over the years I got, say, five disks of varying quality - I shouldn't add them to a pool as five individual vdevs :)

> if any single vdev dies - whole pool dies. Do i remember this correctly?

Yes, that's why you don't have single-disk vdevs.

Re: OpenZFS – add disks to existing RAIDZ

#118
post #72

Earlier quoted context omitted.

....vs stressing all of them for parity rebuild.

Wouldn't it be better to apply stress over more drives to minimize the chances that you lose a second drive during a rebuild?

I believe this is the article I read when I started:

https://jrs-s.net/2015/02/06/zfs-you-should-use-mirror-vdevs...

Re: OpenZFS – add disks to existing RAIDZ

#119
post #49

I’m not an expert whatsoever but what I’ve been doing for my NAS is using mirrored VDEVs. Started with one and later on added a couple more drives for a second mirror. Coincidentally one of the drives of my 1st mirror died few days ago after rebooting the host machine for updates and I replaced it today, it’s been resilvering for a while.

I’ve read this is suboptimal because you are now stressing the drive that has the only copy of your data to rebuild. what are your thoughts?

I am backing up the whole NAS in case such a failure happens, and as was mentioned in other replies getting the replacement drive in the pool is way quicker on a mirrored vdev.

Re: OpenZFS – add disks to existing RAIDZ

#120
post #56
post #30

I wish Apple and Oracle would have just sorted things out and made ZFS the main filesystem for the Mac. Way back in the day when they first designed Time Machine, it was supposed to just be a GUI for ZFS snapshots. How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). I could buy a new external disk, add it to a pool, have seamless storage expansion. It would be great. Ah, what coul…

Yes, this will always depress me, and to me personally be one of the ultimate evils of the court invented idea of "software patents". I've used ZFS with Macs sicne 2011, but without Apple onboard it's never been as smooth as it should have been and has gotten more difficult in some respects. There was a small window where we might have had a really universal, really solid FS with great data guarantees and features. A…

1000x this. A universal filesystem for UNIX would have been a wonderful thing, and would have been the best legacy Sun could have left.
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