[prev in list] [next in list] [prev in thread] [next in thread] 

List:       freebsd-fs
Subject:    Re: ZFS send problem
From:       Albert Shih <Albert.Shih () obspm ! fr>
Date:       2018-06-19 8:11:24
Message-ID: 20180619081124.GA7228 () io ! chezmoi ! fr
[Download RAW message or body]

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
_______________________________________________
freebsd-fs@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-fs
To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
[prev in list] [next in list] [prev in thread] [next in thread]