[dm-devel] Promise and ALUA

[Xose Vazquez Perez]

On 8/16/20 4:30 AM, McIntyre, Vincent (CASS, Marsfield) wrote:

> Promise recommend the multibus option,

Promise docs are a bit messy. The multibus example is a mistake.

There are only two options for this array: failover or group_by_prio.
There are plenty of examples, for old distributions, at
"Linux PerfectPath - Promise Multipath Driver", under:
https://www.promise.com/Support/DownloadCenter/VTrak/Ex30/E830f#Utilities

> Thanks for your analysis. The model is VTrak E830f (VTE830fD).
> The unit is definitely set to active-active controllers.

Yep, it's a dual controller array. But the controllers are no able to
access to a LUN at the same time, and from all paths.

Only high-end arrays(3PAR, Symmetrix, DS8000, ONTAP, VSP, ...) do this.

In VTrak arrays, one LUN is owned only by one controller.

> The firmware could use an update however, the latest release
> seems to have been overlooked. I'll try updating and look
> into enabling ALUA support.

If ALUA is not used, multipathd must be configured with the
"failover" option for "path_grouping_policy"

> One question about the man page though.
> it seems from the current text that putting
>    hardware_handler     "0"
> in the config would be ignored for arrays that are
> assumed to have ALUA support.
> However if the array has ALUA support turned off and
> multipathd detects this, then the package falls back to using
>    hardware_handler     "0"
> of its own accord?
> If that's correct, could that be added to the man page?

Debian 10 is using a very old multipath-tools release (0.7.9 - nov 2018)
without any upstream fixes. I don't know if it's an old bug or
the default setting "hardware_handler = 1 alua" was interfering.