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From: Martin Wilck <martin.wilck@suse.com>
To: "bmarzins@redhat.com" <bmarzins@redhat.com>,
	"christophe.varoqui@opensvc.com" <christophe.varoqui@opensvc.com>
Cc: "dm-devel@redhat.com" <dm-devel@redhat.com>
Subject: Re: [dm-devel] [PATCH 0/9] Add protocol specific config subsection
Date: Tue, 12 Apr 2022 10:31:50 +0000	[thread overview]
Message-ID: <95a66d760a1ad8ac943de611ebb3e61d5a41afdb.camel@suse.com> (raw)
In-Reply-To: <1649728799-11790-1-git-send-email-bmarzins@redhat.com>

On Mon, 2022-04-11 at 20:59 -0500, Benjamin Marzinski wrote:
> Some storage arrays can be accessed using multiple protocols at the
> same
> time.  I've have customers request the ability to set different
> values
> for the path specific timeouts, like fast_io_fail_tmo, based on the
> protocol used to access the path. In order to make this possible,
> this
> patchset adds a new protocol subsection to the device subsection and
> the
> overrides section. This allows users to set a device config's path
> specific timeouts, such as dev_loss_tmo, fast_io_fail_tmo, and
> eh_deadline on a per-protocol basis.

Sigh... I am not happy about this amount of additional complexity in
the multipath configuration. It is already so complicated that hardly
anyone really understands how it works.

I fully agree that some properties, in particular fast_io_fail_tmo [1],
are rather properties of protocol or fabrics than a storage array.
But do we really need to differentiate by both "device" and "protocol"?
IOW, do users need different fast_io_fail_tmo value for the same
protocol, but different arrays? My feeling is that making this property
depend on a 2-D matrix of (protocol x storage) is overcomplicating
matters. And _if_ this is necessary, what do we gain by adding an
"overrides" on top? [2]

What about adding simply adding "protocols" as a new top section in the
conf file, and have the per-protocol settings override built-in hwtable
settings for any array, but not explicit storage-device settings in the
conf file?

Regards,
Martin

[1]: wrt dev_loss_tmo, I tend to think that the best value must be
found based on neither protocol nor array, but data center staff.
[2]: I strongly dislike "overrides", in general. I wonder what we need
it for, except for quick experiments where people are too lazy to add
explicit settings for devices and/or multipaths.

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  parent reply	other threads:[~2022-04-12 10:32 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-12  1:59 [dm-devel] [PATCH 0/9] Add protocol specific config subsection Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 1/9] libmultipath: steal the src string pointer in merge_str() Benjamin Marzinski
2022-04-12 10:38   ` Martin Wilck
2022-04-12  1:59 ` [dm-devel] [PATCH 2/9] libmultipath: make protocol_name global Benjamin Marzinski
2022-04-12 10:40   ` Martin Wilck
2022-04-12  1:59 ` [dm-devel] [PATCH 3/9] libmultipath: add a protocol subsection to multipath.conf Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 4/9] libmultipath: Set the scsi timeout parameters by path Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 5/9] libmultipath: check the hwentry pctable for path variables Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 6/9] libmultipath: make snprint_pctable indent a variable amount Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 7/9] libmultipath: add procotol subsection to overrides Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 8/9] libmultipath: fix eh_deadline documentation Benjamin Marzinski
2022-04-12  1:59 ` [dm-devel] [PATCH 9/9] libmultipath: Add documentation for the protocol subsection Benjamin Marzinski
2022-04-12 10:31 ` Martin Wilck [this message]
2022-04-12 13:18   ` [dm-devel] [PATCH 0/9] Add protocol specific config subsection Martin Wilck
2022-04-12 18:47   ` Benjamin Marzinski
2022-04-12 20:47     ` Martin Wilck
2022-04-12 22:01       ` Benjamin Marzinski
2022-04-13 11:03         ` Martin Wilck

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