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Re: why is zfs taking 6 seconds to unmount each filesystem, to export pool?

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Does anyone here at d-u (sid) know why zpool export is doing its umounts __really__ slowly?


(btw, anyone wanting to dip their toes in the clear zfs waters might want a little tutorial recently written for a few basic zfs steps:
  ZFS Cheatsheet + Backups tutorial
  https://github.com/zenaan/quick-fixes-ftfw/blob/master/zfs/zfs.md
)



----- Forwarded message from Ivan Volosyuk <ivan.volosyuk@gmail.com> -----

From: Ivan Volosyuk <ivan.volosyuk@gmail.com>
To: Discuss <zfs-discuss@list.zfsonlinux.org>
Reply-To: Discuss <zfs-discuss@list.zfsonlinux.org>
Date: Sun, 5 Jul 2020 22:49:19 +1000
Subject: Re: [zfs-discuss] why is zfs taking 6 seconds to unmount each filesystem, to export pool?
List-Id: "Discuss" <zfs-discuss.list.zfsonlinux.org>

Looks like bad interaction with systemd. I don't delegate to systemd
for mounting datasets and the operation is pretty much instant. I
didn't try systemd zfs mount generator.

On Sun, Jul 5, 2020 at 7:24 PM Zenaan Harkness <zen@freedbms.net> wrote:
>
> Why does zfs take about 6 seconds per filesystem, to unmount each, just to export a single disk pool, when that pool had only just been imported and had no activity?
>
> Since the pool has about 60 filesystems, this means ~6 minutes of unmounts before I can "safely" unplug this disk, which is user un-friendly.
>
> (The disk was attached via USB3.)
>
> This is repeatable.
>
>
> Command:
>
> # zpool export L-zen-setups
> ------->> 20200705@19:08:44 <<-------
> ≡ 1  root@eye 20200705@19:15:52 ~
> 
> (We can see this cmd took ~7 minutes to run.)
> 
> Sample syslog:
> Jul 05 19:08:44 eye systemd[2111]: Library-Lpools-zen-p1\x2dsetups_misc-video.mount: Succeeded.
> Jul 05 19:08:44 eye systemd[1260]: Library-Lpools-zen-p1\x2dsetups_misc-video.mount: Succeeded.
> Jul 05 19:08:44 eye systemd[1]: Library-Lpools-zen-p1\x2dsetups_misc-video.mount: Succeeded.
> Jul 05 19:08:47 eye systemd[2111]: Library-Lpools-zen-p1\x2dsetups_misc-src.mount: Succeeded.
> Jul 05 19:08:47 eye systemd[1260]: Library-Lpools-zen-p1\x2dsetups_misc-src.mount: Succeeded.
> Jul 05 19:08:47 eye systemd[1]: Library-Lpools-zen-p1\x2dsetups_misc-src.mount: Succeeded.
> 
> ...
> Jul 05 19:15:39 eye systemd[1]: Library-Lpools-zen-p1\x2dsetups_misc-backups.mount: Succeeded.
> Jul 05 19:15:39 eye systemd[1260]: Library-Lpools-zen-p1\x2dsetups_misc-backups.mount: Succeeded.
> Jul 05 19:15:45 eye systemd[2111]: Library-Lpools-zen-p1\x2dsetups_misc.mount: Succeeded.
> Jul 05 19:15:45 eye systemd[1]: Library-Lpools-zen-p1\x2dsetups_misc.mount: Succeeded.
> Jul 05 19:15:45 eye systemd[1260]: Library-Lpools-zen-p1\x2dsetups_misc.mount: Succeeded.
> Jul 05 19:15:52 eye zed[2123304]: eid=2224 class=pool_export pool_guid=0x012FC06FFAFBEE35
> Jul 05 19:15:52 eye zed[2123307]: eid=2225 class=config_sync pool_guid=0x012FC06FFAFBEE35
> 
> ??

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Re: why is zfs taking 6 seconds to unmount each filesystem, to  export pool? Zenaan Harkness <zenaan@freedbms.net> - 2020-07-06 06:30 +0200
  Re: why is zfs taking 6 seconds to unmount each filesystem, to  export pool? Andrei POPESCU <andreimpopescu@gmail.com> - 2020-07-06 08:00 +0200

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