[Lustre-discuss] MD1000 woes and OSS migration suggestions

Andreas Dilger adilger at sun.com
Wed Dec 30 14:44:49 PST 2009

On 2009-12-29, at 19:33, Nick Jennings wrote:
> Hi Everyone,

Hi Nick,

> We've been using an MD1000 as our storage array for close to a year
> now, just hooked up to one OSS (LVM+ldiskfs). I recently ordered 2  
> more
> servers, one to be hooked up to the MD1000 to help distribute the  
> load,
> the other to act as a lustre client (web node).
> The hosting company informs me that the MD1000 was never setup to
> operate in split mode (which I asked for in the beginning) so  
> basically
> only one server can be connected to it.
> I now am faced with a tough call, we can't bring the filesystem down
> for any extended period of time (a few minutes is OK, though 0  
> downtime
> would be perfect!) and I'm not sure how to proceed in a way that would
> make things cause the least amount of headache.
> The only thing I can think of is to set up a second MD1000 (configured
> for split mode) connect it to OSS2 (the new one which is not yet being
> used), add it to the Lustre filesystem and then somehow migrate the  
> data
> from OSS1 (old MD1000) to OSS2 (new MD1000) ... then, bring OSS1
> offline, and connect it to the second partition of new MD1000 and  
> bring
> that end online once more.

There is a section in the manual about "manual data migration", which  
should let you move the data.  Note that this is not 100% transparent  
to applications, but it is safe if you know either that files are  
unused, or only open for reading.

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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