[Lustre-discuss] MGS and MDT on Failover Pair

Roger Spellman roger at terascala.com
Wed Sep 10 13:23:46 PDT 2008


I am building a system with a redundant MDS, that is two MDS sharing a
set of disks, one being Active, the other Standby.
 
If I put the MGS and MDS on the same system, it appears that they must
be on the same partition as well.  Otherwise, when there is a failover,
the MGS will not fail over.  Is that true?

Assuming that it is true, then I mount the MGS/MDT partition first, then
all the OSTs.
 
When I unmount, I usually want to unmount the MDT prior to unmounting
the OSTs, because the MDT is a client of the OSTs.  Is that possible
here?  In other words, I want to stop the MDT service first, then
unmount the OSTs, then unmount the MGS.  How can I stop the MDT service?

If I don't do this, that is, if I just unmount the OSTs followed by the
MGS/MDT, then I get errors like this:
 
Lustre: raid6-OST0002-osc: Connection to service raid6-OST0002 via nid
10.2.46.74 at o2ib <mailto:10.2.46.74 at o2ib>  was lost; in progress
operations using this service will wait for recovery to complete.
. . .
LustreError: 8964:0:(lov_obd.c:418:lov_disconnect_obd()) Target
raid6-OST0000_UUID disconnect error -5
LustreError: 8964:0:(lov_obd.c:418:lov_disconnect_obd()) Target
raid6-OST0002_UUID disconnect error -5
Lustre: Request x105 sent from raid6-OST0003-osc to NID 10.2.46.75 at o2ib
<mailto:10.2.46.75 at o2ib>  5s ago has timed out (limit 5s).
. . .
Lustre: MGS has stopped.
Lustre: Mount still busy with 7 refs, waiting for 330 secs...


So, my question is:  Is there a way to stop just the MDT function PRIOR
to unmounting the OSTs?
 
Thanks.
 
-Roger
 
Roger Spellman
Staff Engineer
Terascala, Inc.
508-588-1501
www.terascala.com <http://www.terascala.com/> 
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