[Lustre-discuss] Could "Client & MGS" or "Client & OSS" running at one node together?

Brian J. Murrell brian at whamcloud.com
Mon Mar 12 14:35:12 PDT 2012


On 12-03-06 12:01 AM, zhengfeng wrote:
> 
> Since there is no more node in our project when using Lustre, I want to confirm that:
> 
> 1) Could the "Client" and "MGS" run at one node together? or could "Client" and "OSS" run at one node together?

Theoretically, the client and OST cannot be on the same node due to a
potential memory deadlock.  When a node that is a Lustre client grows
short of memory it flushes it's cache to free some memory up.

However if the OST that it needs to flush pages to is also on the same
node, it will need to to allocate memory to receive the pages from the
client, which it will not be able to do since the node is already short
of memory which is causing the need for the client to flush.

Cheers,
b.

-- 
Brian J. Murrell
Senior Software Engineer
Whamcloud, Inc.

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