Storage 'failover' largely kills FreeBSD 10.x under XenServer?

[Miroslav Lachman]

Karl Pielorz wrote on 2017/09/20 16:54:
>
>
> --On 20 September 2017 at 12:44:18 +0100 Roger Pau Monné
> <roger.pau at citrix.com> wrote:
>
>>> Is there some 'tuneable' we can set to make the 10.3 boxes more tolerant
>>> of the I/O delays that occur during a storage fail over?
>>
>> Do you know whether the VMs saw the disks disconnecting and then
>> connecting again?
>
> I can't see any evidence the drives actually get 'disconnected' from the
> VM's point of view. Plenty of I/O errors - but no "device destroyed"
> type stuff.
>
> I have seen that kind of error logged on our test kit - when
> deliberately failed non-HA storage, but I don't see it this time.
>
>> Hm, I have the feeling that part of the problem is that in-flight
>> requests are basically lost when a disconnect/reconnect happens.
>
> So if a disconnect doesn't happen (as it appears it isn't) - is there
> any tunable to set the I/O timeout?
>
> 'sysctl -a | grep timeout' finds things like:
>
>   kern.cam.ada.default_timeout=30


Yes, you can try to set kern.cam.ada.default_timeout to 60 or more, but 
it can has downside too.

Miroslav Lachman