[Lustre-discuss] Lustre Thumper Fault Tolerance

[Klaus Steden]

Andreas,

Is the mmp feature already in the existing Lustre distribution? If so, what
versions are mmp-aware? If not, which version will be the first to
incorporate it?

thanks,
Klaus 

On 3/10/08 2:15 PM, "Andreas Dilger" <adilger at sun.com>did etch on stone
tablets:

> On Mar 10, 2008  09:09 -0600, Colin Faber wrote:
>> Is this true even in the case of mounting the OSS as a read only node?
> 
> Yes, definitely even a "read only" mount can cause serious corruption.
> There are several issues involved, the most dangerous is that even for
> read-only mounting the journal is replayed by the kernel or otherwise
> the filesystem may appear to be corrupted.
> 
> In addition, there is the problem that (meta)data that is cached on the
> read-only mounting node will become incorrect as the writing node is
> changing the filesystem.  The ext3 filesystem is not cluster aware.
> 
> In order to prevent situations like this, the newer releases of ldiskfs
> and e2fsprogs have an "mmp" (multi-mount protection) feature which will
> prevent the filesystem to be mounted on another node if it is active
> on one node (either mounted, or running e2fsck).
> 
> This will be enabled by default on newly-formatted filesystems which
> are created with the "--failover" flag, and can also be enabled by
> hand with "tune2fs -O mmp /dev/XXXX" (replace with MDT or OST device
> names as appropriate).  This will prevent the filesystem from being
> mounted or e2fsck'd by old kernels/e2fsprogs so it isn't enabled by
> default on existing filesystems.
> 
>> Andreas Dilger wrote:
>>> On Mar 07, 2008  00:04 +0530, Neeladri Bose wrote:
>>>   
>>>> To address the performance hit (whatever be the %age) if we setup DRDB in
>>>> active-passive mode across the 4500's but have the LustreFS points to
>>>> separate raid sets from the network across the DRDB pair of 4500's & thus
>>>> become an active-active solution which may actually increase the
>>>> throughput of the LustreFS.
>>>> 
>>>> Can it be a possible scenario using DRDB on Linux with ext3 & LustreFS?
>>>>     
>>> 
>>> No, Lustre does not support active-active export of backing filesystems.
>>> This doesn't work because the backing filesystems (ext3/ZFS) are not
>>> themselves cluster-aware and mounting them on two nodes will quickly
>>> lead to whole filesystem corruption.
> 
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
> 
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