galitz wrote:
I am evaluating iSCSI in our production environment and have a
question.
When I induce a failure by powering down the iSCSI target while there
is active traffic and then restore the iSCSI target 5+ minutes later,
the filesystem remains in read-only mode. Fair enough, I see by
reading the docs that anytime a filesystem error is generated the
filesystem is made read-only.
I can clear this by ummounting and then remounting the filesystem. Is
there a more elegant or a recommended way of restoring the filesystem
to a read-write state once the iSCSI target has returned to service?
Ideally we'd like this to be a transparent process. Perhaps dm-
multipath is what I need?
I think dm-multpath is best. But if you setup dm-multipath to eventually
return IO errors to the layer above it, then you will have the same problem.
At the iscsi layer you can set node.session.timeo.replacement_timeout to
a higher value and that is how long we will hold onto IO before failing
it (default is 2 minutes). There is a bug in this code where we can only
hold on to it for so long. I just did this patch against 269.2 which
allows you to set the node.session.timeo.replacement_timeout to 0 which
will hold onto the IO until we reconnect.
At the dm multipath layer you can set the no_path_retry to do the same
thing. If you set this to queue it will hold onto IO forever or until
the user intervenes.
But like I said if you get FS errors then you have to unmount and
remount. If your questions was about that then there is nothing I can do.
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Only in open-iscsi-2.0-869.2.tmo/kernel: Module.markers
Only in open-iscsi-2.0-869.2.tmo/kernel: modules.order
diff -aurp open-iscsi-2.0-869.2/kernel/scsi_transport_iscsi.c
open-iscsi-2.0-869.2.tmo/kernel/scsi_transport_iscsi.c
--- open-iscsi-2.0-869.2/kernel/scsi_transport_iscsi.c 2008-05-08
19:53:48.0 -0500
+++ open-iscsi-2.0-869.2.tmo/kernel/scsi_transport_iscsi.c 2008-06-23
16:03:20.0 -0500
@@ -431,8 +431,10 @@ static void __iscsi_block_session(struct
session-state = ISCSI_SESSION_FAILED;
spin_unlock_irqrestore(session-lock, flags);
scsi_target_block(session-dev);
- queue_delayed_work(iscsi_eh_timer_workq, session-recovery_work,
- session-recovery_tmo * HZ);
+ if (session-recovery_tmo 0)
+ queue_delayed_work(iscsi_eh_timer_workq,
+ session-recovery_work,
+ session-recovery_tmo * HZ);
}
void iscsi_block_session(struct iscsi_cls_session *session)
@@ -1089,8 +1091,7 @@ iscsi_set_param(struct iscsi_transport *
switch (ev-u.set_param.param) {
case ISCSI_PARAM_SESS_RECOVERY_TMO:
sscanf(data, %d, value);
- if (value != 0)
- session-recovery_tmo = value;
+ session-recovery_tmo = value;
break;
default:
err = transport-set_param(conn, ev-u.set_param.param,
diff -aurp open-iscsi-2.0-869.2/usr/initiator.c
open-iscsi-2.0-869.2.tmo/usr/initiator.c
--- open-iscsi-2.0-869.2/usr/initiator.c2008-05-08 19:53:48.0
-0500
+++ open-iscsi-2.0-869.2.tmo/usr/initiator.c2008-06-23 16:05:43.0
-0500
@@ -523,13 +523,6 @@ __session_create(node_rec_t *rec, struct
else
session-initiator_alias = dconfig-initiator_alias;
- /* session's eh parameters */
- session-replacement_timeout = rec-session.timeo.replacement_timeout;
- if (session-replacement_timeout == 0) {
- log_error(Cannot set replacement_timeout to zero. Setting
- 120 seconds\n);
- session-replacement_timeout = DEF_REPLACEMENT_TIMEO;
- }
session-fast_abort = rec-session.iscsi.FastAbort;
session-abort_timeout = rec-session.err_timeo.abort_timeout;
session-lu_reset_timeout = rec-session.err_timeo.lu_reset_timeout;
