Date: Tue, 19 Jun 2018 10:11:24 +0200 From: Albert Shih <Albert.Shih@obspm.fr> To: freebsd-fs@freebsd.org Subject: Re: ZFS send problem Message-ID: <20180619081124.GA7228@io.chezmoi.fr> In-Reply-To: <20180614175445.GA1781@io.chezmoi.fr> References: <20180614175445.GA1781@io.chezmoi.fr>
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Le 14/06/2018 à 19:54:45+0200, Albert Shih a écrit
> Hi,
>
> I still got a very serious problem with zfs send (not recv).
>
> After I take a snapshot and try to send it, the server begin to send the
> snapshot (I can see on the target the incomming data) and after sometime
> (5=10m) on the server the zfs command freeze, I can launch zpool command
> either.
>
> I check arc size, and if I let the max amount of memory to the
> vfs.zfs.arc_max (~ Max RAM ~ 192Go) the zfs command freeze simultaneously
> with the arc reach 100.3% of the max (but I cannot make lots of test, so
> I'm not sure it's related).
>
> If I set le vfs.zfs.arc_max at half of the RAM ( = 96Go) I can see thought
> zfs-stats the arc come to 100.3% and empty to 98-99% and raise again.
> Either way the zfs command not really freeze totally but take lot of time
> to answer (~10-20 seconds when normally it's < 1sec).
>
> The only « special » configuration (vs my other server doing same thing
> without problem) is I got two zpool on this one. I've no idea if that can
> be a problem (one with 2 ssd, the other with 4 vdev of 7 disks)
>
> I check dmesg, /var/log/all.log and don't find any information or error
> message.
>
So I eventually find a solution to my problem, I don't know if it's a bug
(I can do a bug report), any way, I would love if anyone can give me a explanation
To fix the problem with the zfs send I need to disable prefetch by adding
sysctl -w vfs.zfs.prefetch_disable=1
with that option the zfs didn't hang anymore.
Regards
--
Albert SHIH
Observatoire de Paris
xmpp: jas@obspm.fr
Heure local/Local time:
Tue Jun 19 10:07:47 CEST 2018
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