what is lvm swith over time

[swarup sekhar]

i have one lun presented via two paths in a particular host.

added both the paths in vg ( one is primary and another as alternative link )

when I wanted to do vgreduce to the primary link LVM shud automatically switch over to the alternative link..

Can anybody tell me what is the default time taken to LVM switch over from one PV to another.

10 points to all the reply

Thanks in advance.

[Mustafa Gulercan · Accepted solution]

you can increase the timeout value.

increasing the time out value to
90 seconds with:

pvchange -t

It is recommended to monitor the load, check the SCSI, cable and
termination components and install the latest patches. The time out
value could be increased up to 180 seconds.

regards;
mustafa

[Mustafa Gulercan]

On lvols which have a filesystem NEVER set an lvtimeout !!

If the time the lower layer needs to recover from a primary link failure
(pvtimeout plus switching time) exceeds the lvtimeout-time LVM sends an error
to the upper layer.
If the upper layer is a filesystem that results in write/read errors and
corruption will occure.
When the lvol is a raw-volume then the upper layer is an application (for
example oracle or sybase) which has to manage the error.
If the application vendor needs to use raw-lvols with lvtimeouts, the lvtimeout
has to be adjusted with the pvtimeout to give LVM enough time to recover from a
link failure. lvtimout > (pvtimeout + switching time)

[swarup sekhar]

Thanks mustafa,

I want the switching time ...not the pv timeout what u have mentioned...

Thanks
Swarup

[Bill Costigan]

It's about the same thing. When an I/O timesout (PV timeout)LVM will try the I/O on an alternate link.

[Ganesh Balraman]

Dear Sir,

Lvm Timeout for alternate link will be always read it from pvtime out only.

Example : pvchange -t < time >.

Regds
Ganesh

[Raj D.]

Swarup,
Default timeout is 60 seconds , but you can set it with pvchange -t option.

Ex: #pvchange -t IO_timeout_sec /dev/dsk/cxtxdx

hth,
Raj.