[lustre-discuss] confused about mdt space

Mohr Jr, Richard Frank rmohr at utk.edu
Wed Apr 1 07:59:43 PDT 2020

> On Apr 1, 2020, at 10:07 AM, Mohr Jr, Richard Frank <rmohr at utk.edu> wrote:
>> On Apr 1, 2020, at 3:55 AM, 肖正刚 <guru.novice at gmail.com> wrote:
>> For  " 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" :
>> I checked the inode size is 1KB and  in my online systems,  as you said , about 40~41% of mdt disk space consumed by inodes. 
>> but from the manual I found the default "inode ratio" is 2K, so where the additional 0.5KB comes from ?
> I was basing this on info I found in this email thread:
> http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2018-February/015302.html
> I think the 2K/inode ratio listed in the manual may be incorrect (or perhaps someone can point out my mistake).

Looking at the lustre source (utils/libmount_utils_ldiskfs.c), the default behavior is determined by this line:

		bytes_per_inode = inode_size + 1536

So the default bytes per inode is 1K (inode size) + 1.5K = 2.5K

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

More information about the lustre-discuss mailing list