[Lustre-discuss] disappeared data from OST

Mag Gam magawake at gmail.com
Tue Feb 16 18:52:11 PST 2010


Peter:

I am glad you mention this.

What is an appropriate backup tool for Lustre? I know with 2.x they
will introduce ChangeLogs, but for people using 1.6.x what is a good
tool? I suppose 'rsync' or drbd for realtime?  What do you recommend?



On Mon, Feb 15, 2010 at 6:30 PM, Peter Grandi <pg_lus at lus.for.sabi.co.uk> wrote:
>
>> After a power spike this weekend that crashed several machines
>> (not the OSS'es...) and/or possibly hitting 100% file space
>> usage on one of them (we have been dangerously close for a
>> while), it hung this morning.
>
> That's fairly clear, but did you do any checks as to whether all
> the drives involved are entirely error free? How do you know
> your storage system is still good to use?
>
> Also did you have battery backup for at least the storage HAs?
>
>> After restarting, it showed many files as missing. [ ... ]
>> Now I am afraid that if I carry on (probably just cycling the
>> power, since "reboot" also hangs), it will come back in the
>> same state, i.e. 95% of the data gone. Is this already
>> irreparably the case, or am I just paranoid?  Any suggestions
>> would be appreciated (in other words: HELP!!!!).
>
> There is one simple solution: restore backups. That's what they
> are for, situations like this. It is probably much faster than
> any attempt at recovery, if the backups are on suitable media.
> I think that in many cases restoring from backup is faster than
> running 'fsck' over damaged filesystems.
>
> As to that, I reckon that it is often little appreciated that
> the most cost effective way to backup efficiently a large Lustre
> storage pool may be another Lustre storage pool, and Lustre can
> make pretty good backup servers (excellent sequential write
> rates from cheap low IOPS drives, over Ethernet).
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