On 04/04/2013 12:59 PM, Alejandro Comisario wrote:
> Mike, i think something is wrong and i dont seem to know what, because
> still, im getting I/O errors reported to the filesystem layer after 120
> seconds, but i dont know if its from the iscsi side or other
> configuration is involved, this is what we negotiated with the target :
> 
> root@DC2-r16-22vms:/var/log# iscsiadm -m node -T
> iqn.1992-08.com.netapp:sn.1574861693
> # BEGIN RECORD 2.0-871
>

These values are what we request from the target. iscsiadm -m session -P
2 is what we are currently using.


> node.session.timeo.replacement_timeout = 600

replacement timeout though is not something we negotiate with the
target, so we should be using that value.

> 
> We issued a dd against the ext4 LUN mounted, but after 120 seconds we
> see this errors in /var/log/syslog :


> 
> Apr  4 10:33:41 DC2-r16-22vms iscsid: Kernel reported iSCSI connection
> 3:0 error (1011) state (3)

Here we see the initial error. When this happens we start the
replacement_timeout/recovery_timeout timer.

> Apr  4 10:37:17 DC2-r16-22vms kernel: [71981.018502] INFO: task
> jbd2/sdc1-8:100283 blocked for more than 120 seconds.
> Apr  4 10:37:17 DC2-r16-22vms kernel: [71981.018505] "echo 0 >
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.


This and the trace after it is not a error. It is just a warning. There
is a hung_task_timeout_secs timer as you see below. If a IO does not
complete for that amount of seconds the kernel will send this warning.
If you expect IO to hang for longer periods then you should change that
value like is describes below.


> last error at 1365011431: ext4_put_super:819
> Apr  4 10:43:42 DC2-r16-22vms kernel: [72365.960932]  session3: session
> recovery timed out after 600 secs

Here is where we see IO errors. You set the timer to 600 secs and so
about 10 minutes after we see the connection error above we see this.
This is and the messages after is what indicates real IO errors.

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