From: Hannes Reinecke <hare@suse.de>
To: Xose Vazquez Perez <xose.vazquez@gmail.com>
Cc: dm-devel@redhat.com
Subject: Re: [PATCH 3/3] multipathd: Add 'sysfs' prioritizer
Date: Wed, 9 Nov 2016 07:49:11 +0100 [thread overview]
Message-ID: <a6e52ead-dda3-13e5-c033-2719102aeaa9@suse.de> (raw)
In-Reply-To: <60729efa-12ad-aa28-f657-1b8ec6dbd4d2@gmail.com>
On 11/08/2016 07:52 PM, Xose Vazquez Perez wrote:
> On 07/15/2016 08:48 AM, Hannes Reinecke wrote:
>
>> Recent kernels have an 'access_state' attribute which allows
>> us to read the asymmetric access state directly from sysfs.
>
> Hi Hannes,
>
> with this patch it's impossible to select/autodetect ALUA.
> sysfs always takes precedence over alua.
>
> "detect_prio no" was added to overrides section, to make
> it work again.
>
> SLES 12-SP2
>
> Thank you.
>
But this was precisely the idea.
(After all, it says 'auto-detect', right?)
For ALUA-capable arrays we have a reliable priority detection with the
ALUA device-handler.
So it's far preferable to use the sysfs-provided information (as they
are populated by the ALUA device-handler); the ALUA prioritizer in
multipath-tools will be used as a fallback in case the device handler
isn't loaded or the sysfs files are not present.
Using the sysfs handler has the neat side effect that you don't need to
do I/O for detecting the priority, thereby eliminating one possible
cause for multipath being stuck during failover.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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next prev parent reply other threads:[~2016-11-09 6:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-15 6:48 [PATCH 0/3] sysfs prioritizer Hannes Reinecke
2016-07-15 6:48 ` [PATCH 1/3] libmultipath: call get_vpd_uid() if no uid_attribute is set Hannes Reinecke
2016-07-15 6:48 ` [PATCH 2/3] alua prioritizer: Fix typo 'perf' Hannes Reinecke
2016-07-15 6:48 ` [PATCH 3/3] multipathd: Add 'sysfs' prioritizer Hannes Reinecke
2016-11-08 18:52 ` Xose Vazquez Perez
2016-11-09 6:49 ` Hannes Reinecke [this message]
2016-12-07 18:34 ` Xose Vazquez Perez
2016-07-22 9:44 ` [PATCH 0/3] sysfs prioritizer Christophe Varoqui
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