Attention those who use ESX with SANs

[gogogo5]

On page 118 of the SAN Configuration Guide PDF the last section states:

ESX Configuration - set the following Advanced Settings for the ESX Server host:

Set Disk.UseLunReset to 1[/b]

Set Disk.UseDeviceReset to 0[/b]

Have any of you ppl actually implemented this when using your SAN? What do these settings really do? If they are important settings, which I guess they must be if they are in the PDF, I am surprised they are tucked away here....

[Paul_Lalonde]

For SAN configurations, it is often undesirable for a host to issue a device reset on the SCSI bus. This configuration adjusts the ESX server to only issue SCSI resets at the logical unit (LUN) level, not at the device level.

Device resets on a SAN will interrupt communications between that device and any other hosts communicating with it. LUN resets are less "disruptive"...

Paul

[gogogo5]

thanks, so I take it you have this set then?

[tuifei]

which config file can set this parameter？

[LarsLiljeroth]

Have you implemented the " Set Disk.UseDeviceReset to 0 " ?

What does it mean that you disable the device reset. There must be a downside since it is not set by deafult or ?

[peetz]

I have both values set to 1 on all of our hosts. However, I'm not aware that we changed any of them from the default!?

What does it mean / what will ESX do if both values are 1?

[bertdb]

I'm under the impression that this only changes the way SCSI bus resets on a virtual machines SCSI bus are translated to a real device. Those bus resets are used to clear SCSI reservations, and should indeed be translated into LUN resets (clearing the SCSI reservation of a single LUN), not device resets (clearing all SCSI reservations on that SP/disk array).

[Jae_Ellers]

#!/bin/sh

esxcfg-advcfg -s 0 /Disk/UseDeviceReset

esxcfg-advcfg -s 1 /Disk/UseLunReset

service mgmt-vmware restart