[lustre-discuss] zfs -- mds/mdt -- ssd model / type recommendation

[Isaac Huang]

The dnodes are ditto'ed over whatever redundancy the raidz/mirror
already provides, so for 2-way mirrors that'd be multiplied by 4 from
the compressed dnode size. BTW, all ZFS meta-data are compressed by
default. The recent 0.6.4 release supports LZ4 compression of meta
data, which I found in some benchmarks to increase object
creation/removal rates by roughly 9%. YMMV though.

-Isaac

On Tue, May 05, 2015 at 07:52:16PM +0000, Alexander I Kulyavtsev wrote:
> I checked lustre 1.8.8 ldiskfs MDT: 106*10^6 inodes take 610GB on MDT, or 3.5 KB/inode. I've thought it is less.
> So MDT size just 'factor three' more compared to old ldiskfs.
> How many files do you plan to have?
> Alex.
> 
> On May 5, 2015, at 12:16 PM, Alexander I Kulyavtsev <aik at fnal.gov<mailto:aik at fnal.gov>> wrote:
> 
> I'm presently at about 10 KB/inode which seems too high compared with ldiskfs.
> 

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-- 
-Isaac