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From: Alibek Amaev <alibek.a@gmail.com>
To: Hannes Reinecke <hare@suse.de>
Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: Block device naming
Date: Thu, 16 May 2019 16:49:15 +0300
Message-ID: <CA+TYKz1E3mJ0hDQcv19QAFgeWVA-ADLoHtGQ5hy8SFxHOfuqfQ@mail.gmail.com> (raw)
In-Reply-To: <e81e675e-e084-197a-fc13-101985bde590@suse.de>

I have more example from IRL:
In Aug 2018 I was start server with attached storages by FC from ZS3
and ZS5 (it is Oracle ZFS Storage Appliance, not NetApp and also
export space as LUN) server use one LUN from ZS5. And recently on
server stopped all IO on this exported LUN  and io-wait is grow, in
dmesg no any errors or any changes about FC, no errors in
/var/log/kern.log* /var/log/syslog.log*, no throttling, no edac errors
or other.
But before reboot I saw:
wwn-0x600144f0b49c14d100005b7af8ee001c -> ../../sdc
I try to run partprobe or try to copy from this block device some data
to /dev/null by dd - operations wasn't finished IO is blocked
And after reboot i seen:
wwn-0x600144f0b49c14d100005b7af8ee001c -> ../../sdd
And server is run ok.

Also I have LUN exported from storage in shared mode and it accesible
for all servers by FC. Currently this LUN not need, but now I doubt it
is possible to safely remove it...


On Thu, May 16, 2019 at 3:33 PM Hannes Reinecke <hare@suse.de> wrote:
>
> On 5/16/19 2:26 PM, Alibek Amaev wrote:
> > Hi!
> >
> > I want to address the following problem:
> > On the system with hot-attached new storage volume, such as FC-switch
> > update configuration for connected FC-HBA on servers, linux kernel
> > reorder block devices and change names of block devices. Becouse
> > scsi-id, wwn-id and other is a symbol links to block device names than
> > on change block device name change path to device.
> > This causes the server to stop working.
> >
> > For example, on server present ZFS pool with attached device by scsi-id
> > # zpool status
> >    pool: pool
> >   state: ONLINE
> >    scan: scrub repaired 0 in 1h39m with 0 errors on Sun Oct  8 02:03:34 2017
> > config:
> >
> >      NAME                                      STATE     READ WRITE CKSUM
> >      pool                                      ONLINE       0     0     0
> >        scsi-3600144f0c7a5bc61000058d3b96d001d  ONLINE       0     0     0
> >
> > Before export new block device from storage to hba, scsi-id have next
> > path to device:
> > /dev/disk/by-id/scsi-3600144f0c7a5bc61000058d3b96d001d -> ../../sdd
> >
> > When added new block device by FC-switch, FC-HBA kernel change block
> > device names:
> > /dev/disk/by-id/scsi-3600144f0c7a5bc61000058d3b96d001d -> ../../sdf
> >
> > and ZFS can't access to device until reboot (partprobe, zpool online
> > -e pool scsi-3600144f0c7a5bc61000058d3b96d001d - may help or may not
> > help)
> >
> Hmm. That really is curious; typically existing devices will not be
> reassigned. Especially not if they are in use by something.
> And the FC layer is going into quite some lengths to prevent this from
> happening.
> So this really looks more like an issue with how exactly this 'adding
> new block device' step was done.
>
> > Is there any way to fix or change this behavior of the kernel?
> >
> As I said, this typically does not happen.
> It would need closer examination to figure out what really happened.
>
> > It may be more reasonable to immediately assign an unique persistent
> > identifier of device and linking other identifiers with it?
> >
> Which is what we try ...
>
> > Also I think this is not specific problem of ZFS. And can occur with other
> > file system modules.Moreover, I had previously encountered a similar
> > problem - NetAPP
> > storage attached to servers by FC and export multiple LUN - suddenly
> > decided to change the order of LUNs and Ext4 on servers is switch to
> > readonly mode because driver detect changes of magic number in
> > superblocks of partitions.
> >
> Suddently changing the order of LUNs is _not_ what is supposed to
> happen. This really sounds more like an issue with NetApp.
>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke            Teamlead Storage & Networking
> hare@suse.de                              +49 911 74053 688
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
> HRB 21284 (AG Nürnberg)

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16 12:26 Alibek Amaev
2019-05-16 12:33 ` Hannes Reinecke
2019-05-16 13:49   ` Alibek Amaev [this message]
2019-05-16 14:07     ` Hannes Reinecke
2019-05-17 11:24       ` Alibek Amaev

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