[Lustre-discuss] MD1000 woes and OSS migration suggestions

[Aaron Knister]

Andreas,

Out of sheer curiosity, I was wondering when the "lfs migrate" feature mentioned on the lustre arch wiki might show up :) I can't wait to add it to my lustre utility belt.

-Aaron

On Dec 30, 2009, at 5:44 PM, Andreas Dilger wrote:

> 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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