On 19/10/2018 17:46, Chris.Moore@xxxxxxxxxxxxx wrote:
-----Original Message-----
From: linux-scsi-owner@xxxxxxxxxxxxxxx <linux-scsi-
owner@xxxxxxxxxxxxxxx> On Behalf Of John Garry
Sent: Friday, October 19, 2018 2:19 AM
To: Chris Moore - C33997 <Chris.Moore@xxxxxxxxxxxxx>; hare@xxxxxxx;
linux-scsi@xxxxxxxxxxxxxxx; Jason Yan <yanaijie@xxxxxxxxxx>
Subject: Re: Looking for some help understanding error handling
On 05/10/2018 16:51, Chris.Moore@xxxxxxxxxxxxx wrote:
Thanks Hannes,
After some pointers from Shane Seymour I found that the FC and SRP
transport layers have a devloss timer, so that when a device
disappears they hold on to the target information for a time waiting
to see if it comes back. The SAS transport layer doesn't have that feature.
The options for me then would be to modify scsi_transport_sas.c to
implement the devloss timeout, or to put that functionality into my LLDD.
I'm willing to put the work into the SAS transport and libsas, but I
suspect there's not a universal need for it. And since my LLDD is for
internal use at our company and won't be upstreamed, I'll probably
just do the work there. If anyone feels that this is a feature that more
people would want then I'll look into doing that.
Hello,
This feature sounds interesting for libsas. I however have a question on
feasibility of devloss here (note: I'm not familiar with the concept/realization
for other standards): if a device is deattached and re-attached, how can we
confirm the same device? For SAS device it's ok as a disk has the WWN, but
what about SATA?
Thanks,
John
Would the serial number work? I haven't worked a lot with SATA drives, but
ATA8-ACS says the IDENTIFY DEVICE response must contain a unique serial
number.
I guess in principle it would be possible. The issue is that libsas does
not deal with topics like querying disks. It just deals with SAS layers
below application layer, like link+port managament.
Thanks,
John
