Re: CURRENT: ZFS freezes system beyond reboot

On Mon, 13 Dec 2021 09:30:50 +0200
Andriy Gapon <avg@FreeBSD.org> wrote:

> On 12/12/2021 18:45, Alan Somers wrote:
> > You need to look at what's causing those errors.  What kind of disks
> > are you using, with what HBA?  It's not surprising that any access to
> > ZFS hangs; that's what it's designed to do when a pool is suspended.  
> 
> However, a pool does not have to be suspended on errors.
> failmode property provides a couple of alternatives:
>               wait      Blocks all I/O access until the device connectivity is
>                         recovered and the errors are cleared.  This is the
>                         default behavior.
> 
>               continue  Returns EIO to any new write I/O requests but allows
>                         reads to any of the remaining healthy devices.  Any
>                         write requests that have yet to be committed to disk
>                         would be blocked.
> 
>               panic     Prints out a message to the console and generates a
>                         system crash dump.
> 
> But neither does any magic.
> The errors will still be there.
> 

Hello.

The error's cause was not obvous. I used a SSD, partioned into two halfes, one for ZIL,
the other for L2ARC. When showing "zpool status", the RAIDZ's HDDs (Hitachi/Seagate 4 TB
NAS HDD) where "online", ZIL was "online" and L2ARC device/vdev showd - nothing.

I had to power off/power on the box. For several hours nothing moved on, the box was
frozen, any invocation of any ZFS volume related tool/command hanged the terminal/console.

Several datasets showed errors at <0x0>, nothing serious.

After deleting the ZIL and L2ARC extra SSD from the RAIDZ pool, verything went to normal
again.

It is spooky, if not to say "buggy", if ZFS is capable of freezing the whole box even if
the essential operating system stuff is isolated on a dedicated UFS filesystem.

Kind regards,

O. Hartmann