[Lustre-discuss] howto make a lvm, or virtual lvm?

[Andreas Dilger]

On 2010-12-16, at 7:49, Eudes PHILIPPE <eudes at cisneo.fr> wrote:
> Now, I add a new oss server, with one ost (1GB)
> - On Oss 1, he use 750 Mb of 1000
> - On Oss 2, he use 750 Mb of 1000
> - On Oss 3, he use 0 Mb of 1000
> 
> lfs setstripe -c3 /home on client
> 
> I upload a big file, 1.3 Go
> He write on oss1, 2 and 3, but, when oss 1 and oss2 are full, he stop
> (Couldn't write to remote file "/home/big_log.log": Failure)
> ******************************
> 
> So now, 
> - On Oss 1, he use 1000 Mb of 1000
> - On Oss 2, he use 1000 Mb of 1000
> - On Oss 3, he use 250 Mb of 1000
> I upload again, just for see, my first file (300 MB), he copy the file only
> on Oss3 (oss 1 and 2 are full of course), it's ok :)
> 
> Is there a solution for this problem?

This is much less of a problem in real usage of Lustre, when the size of the file is not a large fraction of thectotal OST size.  Lustre will balance object allocation dynamically based on how full an OST is, but cannot currently do this in the middle of a single file. 

With typical OST sizes in the 8-16TB range today, this is rarely a problem. 

Cheers, Andreas