[Lustre-discuss] lustre file system with failover

Klaus Steden klaus.steden at thomson.net
Thu Jun 12 21:45:55 PDT 2008


Hi Trupti,

It depends on how your failover is implemented. The bottom line is that if
you have a transaction in-flight when your MDT is disconnected, all new
transactions will block until queued and in-flight transactions either
complete or time out. If your failover window is a few seconds or less, you
shouldn¹t notice more than a minor blip as the failover MDS recovers state
for the downed MDS and finishes any transactions in progress.

Your results will vary depending on the hardware you use and the settings of
your failover; in one of my clusters, my failover window is actually quite
long (about a minute and a half) due to the way the storage is implemented
(the FC buses spend considerable time polling each visible LUN looking for
the Lustre ones and I never bothered with device multi-pathing), but my
transactions complete as expected once the MDT becomes active on the
failover MDS.

cheers,
Klaus

On 6/11/08 5:07 AM, "trupti shete" <truptips86 at yahoo.co.in>did etch on stone
tablets:

> Hi
> I am very new to lustre file system.
> I want to know how can I test whether the failover is working or not?
> 
> I am having the following scenario of lustre file system--
> MGS- /dev/sdb on node1 and failnode node2
> MDT- /dev/sdc on node1 and failnode node2
> (I am using iSCSI for the sharing discs /dev/sdb & /dev/sdc between node1 &
> node2)
> OST1- /dev/sda1 on node2
> OST2- /dev/sda2 on node2
> And there are 3 clients.
> 
> If client1 opens a file to write and at that time if I umount the MDT (which
> will be mounted on node1) will node2 take care of? Will client1 experience any
> difference?
> 
> -Trupti
> 
>   
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