[Lustre-discuss] 1.8.1 test setup achieved, what about maximum mdt size

Bernd Schubert bs_lists at aakef.fastmail.fm
Fri Oct 23 02:51:20 PDT 2009


On Tuesday 20 October 2009, Andreas Dilger wrote:
> On 18-Oct-09, at 16:04, Piotr Wadas wrote:
> > Now, I did a simple count of MDT size as described in lustre 1.8.1
> > manual,
> > and setup mdt as recommended. The question is, no matter I did right
> > count
> > or not, what actually will happen, if MDT partition runs out of space?
> > Any chances to dump the whole MGS+MDT combined fs, supply a bigger
> > block
> > device, or extend partition size with some e2fsprogs/tune2fs trick ?
> > This assumes, that no matter how big MDT is, it will be exhausted
> > someday.
> 
> It is true that the MDT device can become full at some point, but this
> happens fairly rarely given that most Lustre HPC users have very large
> files, and the size of the MDT is MUCH smaller than the space needed for
> the file data.  The maximum size of MDT is 8TB, and if you format the

Is that still true with recent kernels such as the one from SLES11? I thought 
ldiskfs is based on ext4 there? So we should have at least 16TiB and I'm not 
sure if all the e2fsprogs patches already have been landed to get 64-bit max 
sizes?


Thanks,
Bernd

-- 
Bernd Schubert
DataDirect Networks



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