[Lustre-discuss] Another server question

Ms. Megan Larko dobsonunit at gmail.com
Tue Feb 3 09:52:01 PST 2009


Hi,

Jumping in here, I see folks saying that taking down a single OSS
causes clients to lose access to that file system until the OSS is
back up and completed recovery.   I will say agree in saying yes for
the the OST's on that OSS.   However other OSTs on different OSS's, if
one set it up that way, will still be accessible.

Our real-world example running 2.6.18-53.1.13.el5  CentOS
lustre.1.6.4.3smp 64-bit (I know it's old; a Lustre upgrade is in my
plans) has an MGS that has three MDTs one each per OSS.  That is usual
and customary.  Currently one OSS failed (power supply unit failure
over last weekend--those go out in groups like car headlights).  I
could not unmount it properly because it cannot be powered up to
respond to any requests.  So I ignore it for now and on the clients I
remove it from the /etc/mtab file.  That is all.   The other OSSes,
with the associated MDTs are fine for the users.

[larkoc at crew01 ~]$ df -h /crew2
Filesystem            Size  Used Avail Use% Mounted on
ic-mds1 at o2ib:/crew2    19T   14T  4.3T  77% /crew2
[larkoc at crew01 ~]$ df -h /crewdat
Filesystem            Size  Used Avail Use% Mounted on
ic-mds1 at o2ib:/crew8    76T   17T   55T  24% /crewdat

We have added storage to an OSS by telling it the MDT and name when
initiating the the array so expansion is possible.   We just did not
configure our Lustre to be a single OSS/MDT set-up.

I have also sucessfully mounted an OSS minus a bad sub-array using the
"Dilger Method" of de-activating the bad OST.  That info was in an
earlier post.  The result was a part of the OSS was available for
recovery/use obtaining information stored only on the remaining OSTs.

I have found the Lustre file system to be very scalable and relatively
robust (my location has experienced some major hardware failures, some
catastrophic, completely outside the range and scope of Lustre).

My $.02

megan



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