[Lustre-discuss] Delete file entries from Metadata server

[Brian J. Murrell]

On Wed, 2009-03-25 at 11:29 -0500, Robert Olson wrote:
> I thought I had read at some point that there is a performance hit
> associated with putting the OST on a LV;

There is nothing particular about an OST on an LV that makes it perform
any worse than anything else on an LV.  That said I don't know what
overhead there is in using an LV over a raw block device.  I've been
using LVs exclusively on all of my (non Lustre) systems for many many
years and I've never felt that they were unacceptably slow.

You might want to benchmark just to have hard numbers on your side.
Benchmarking LVs against the raw block device should be trivial.

> or is that just the case when there are snapshots in play?

Yes, there is definitely a penalty when snapshots are in play since
every write to a block on the origin that has not been written since the
snapshot is actually two writes to copy (or move -- I'm not sure) the
block to the snapshot before writing the new data in the origin.

> Do you recommend using LV's in general when configuring the OST?

We don't recommend one way or the other.  It's really a matter of
personal choice.

b.


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