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List:       lustre-discuss
Subject:    [Lustre-discuss] Misc questions on deployment
From:       dleaberry () iarchives ! com (Daniel Leaberry)
Date:       2006-08-23 11:54:26
Message-ID: 44EC9646.2020300 () iarchives ! com
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Kumaran Rajaram wrote:
> Regarding rebalancing, it would be helpful if a utility to rebalance the
> file-system can be provided. The rebalance utility might be
> time-consuming  which moves objects across OSTs and maps inodes to the
> new location of the objects (in MDS). The rebalance operation might be
> done online in which case the object needs to be locked/unlocked
> before/after migration respectively or offline in which case FS has to
> be unmounted. 
>
> Just a thought..
>
> Regards,
> -Kums 
>   
While out looking at the bugzilla yesterday I found this KB entry on 
rebalancing complete with a rudimentary script. I actually found a lot 
of good answers that weren't in the FAQ in the KB. Thanks for providing 
that resource.

>   
>>>> "Peter J. Braam" <braam@clusterfs.com> 8/22/2006 5:59 PM >>>
>>>>         
> Hi Daniel, 
>
>  > -----Original Message-----
>  > From: lustre-discuss-bounces@clusterfs.com 
>  > [mailto:lustre-discuss-bounces@clusterfs.com] On Behalf Of 
>  > Daniel Leaberry
>  > Sent: Tuesday, August 22, 2006 1:41 PM
>  > To: lustre-discuss@clusterfs.com 
>  > Subject: [Lustre-discuss] Misc questions on deployment
>  > 
>  > We're looking at deploying 1.6 sometime early next year. I 
>  > just have a few questions regarding deployment.
>  > 
>  > 1. How critical is the OS on the OST's. What I mean is 
>  > traditionally I'll have a storage box and the data is always 
>  > separate from the OS. So if I lose the OS I don't really 
>  > care, I re-install and copy back over my /etc/exports file. 
>  > With Lustre I'm not sure I can do that on an OST.
>
> With Lustre you can also - the configuration is stored on the disk. 
> Failover even allows you to do this "live"!
>  
>  > 2. Rebalancing. I did a search and it seems that rebalancing 
>  > is done by hand. IE mv /lustre/data /tmp; mv /tmp/data 
>  > /lustre; I see that 1.6 has support for auto balancing but I 
>  > think that just means it will favor OST's with more space. 
>  > If I use 90% of my cluster on 4 OST's and then add two more 
>  > OST's Those two OST's will handle most of the load until 
>  > they approach the capacity of the other 4. How do other 
>  > people handle rebalancing?
>
> Your understanding of what 1.6 will do is correct.  There will be on
> additional feature coming this fall which allows you to mark certain
> directories (and descendants) to be stored on a particular named
> collection (aka "pool") of OST's.
>
> I cannot really answer how other systems solve this problem.
>
>
> - Peter -
>
>   
Thank you Peter for your answers. The marking of directories for certain 
OST's sounds like exactly what we would use. We process rolls of 
microfilm and for disaster recovery purposes it would work far better if 
each roll was on one OST. Otherwise the loss of an OST would mean we 
could lose 2-3 files per roll which would be terrible.


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