[Pacemaker] iscsi target mounting readonly on client

[Felix Zachlod]

Hello Joseph!

> -----Ursprüngliche Nachricht-----
> Von: Joseph-Andre Guaragna [mailto:joseph-andre at rdmo.com]
> Gesendet: Freitag, 12. April 2013 17:19
> An: pacemaker at oss.clusterlabs.org
> Betreff: [Pacemaker] iscsi target mounting readonly on client

You have to make two things absolutely shure.

1. Data that has been acknowledged by you iscsi Target to your initiator has
hit the device and not only the page cache!

If you run your target in fileio mode you have to use write trough- cause
with write back you or your cluster manager can't ever tell if the writes
have completed before switching the DRBD states.
That will only perform good if you have a decent raid card with BBWC! BUT
YOU MUST RUN WRITE TRHOUGH or blockio (which will be write trough too)
running write back in such a constellation IS NOT SAFE you might risk
SERIOUS DATA CORRUPTION when switching targets.

2. On your initiator side try to rise the /sys/block/sd*/device/timeout
value. That is the time the block device will wait for a command to complete
before handing an i/o error tot he upper layer- which will most probably
lead to your filesystem remounting r/o.

3. This is just a side note: do not use iet. We were running a production
target wit iet for about 2 year which caused horrible problems to us.
Consider scst or lio (I personally do not have any experiences with lio but
scst is running in our production environment for years now without any
problems)

regards
Felix