Date: Sun, 12 Apr 2020 13:54:16 +0200 From: Peter Eriksson <pen@lysator.liu.se> To: freebsd-fs <freebsd-fs@freebsd.org> Cc: Andriy Gapon <avg@FreeBSD.org> Subject: Re: ZFS server has gone crazy slow Message-ID: <F5AD5541-B31A-47B1-A094-18F66E32EA9F@lysator.liu.se> In-Reply-To: <575c01de-b503-f4f9-2f13-f57f428f53ec@FreeBSD.org> References: <2182C27C-A5D3-41BF-9CE9-7C6883E43074@distal.com> <20200411174831.GA54397@fuz.su> <6190573D-BCA7-44F9-86BD-0DCBB1F69D1D@distal.com> <6fd7a561-462e-242d-5057-51c52d716d68@wp.pl> <7AA1EA07-6041-464A-A39A-158ACD1DC11C@distal.com> <FE84C045-89B1-4772-AF1F-35F78B9877D8@lysator.liu.se> <575c01de-b503-f4f9-2f13-f57f428f53ec@FreeBSD.org>
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Hmm. By “ancient” pool version - are you thinking of the one used during FreeBSD 11.0-11.1 days? That was what we were using at the time when we tested “zfs destroy -r foo@bar” vs “zfs destroy -rd foo@bar” and found that “-d” was much quicker.
(We’re now at 11.3 and 12.1 and that whole snapshot cleaning script is completely rewritten and uses a custom “zfs” binary instead that can look at custom user properties to decided which snapshots to delete and not and is much more efficient in general.)
- Peter
> Note, however, that unless you have a very ancient pool version destroying a
> snapshot means that the snapshot object is removed and all blocks belonging to
> the snapshot are queued for freeing. Their actual freeing is done
> asynchronously ("in background") and can be spread over multiple TXG periods.
> That's done regardless of whether -d was used.
>
> --
> Andriy Gapon
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