[lustre-discuss] confused about mdt space

[Mohr Jr, Richard Frank]

> On Mar 30, 2020, at 10:56 PM, 肖正刚 <guru.novice at gmail.com> wrote:
> 
> Hello, I have some question about metadata space.
> 1) I have ten 960GB SAS SSDs for mdt,after done raid10,we have 4.7TB space free.
> after formated as mdt,we only have 2.6TB space free; so where the 2.1TB space go ?
> 2) for the 2.6TB space, what's it used for?

That space is used by inodes.  I believe the recent lustre versions use a 1KB inode size by default and the default format options create 1 inodes for every 2.5 KB of MDT space.  So about 40% of your disk space will be consumed by inodes.

—
Rick Mohr
Senior HPC System Administrator
Joint Institute for Computational Sciences
University of Tennessee