[lustre-discuss] confused about mdt space
adilger at whamcloud.com
Wed Apr 1 23:24:53 PDT 2020
On Apr 1, 2020, at 08:59, Mohr Jr, Richard Frank <rmohr at utk.edu<mailto:rmohr at utk.edu>> wrote:
On Apr 1, 2020, at 10:07 AM, Mohr Jr, Richard Frank <rmohr at utk.edu<mailto:rmohr at utk.edu>> wrote:
On Apr 1, 2020, at 3:55 AM, 肖正刚 <guru.novice at gmail.com<mailto: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:
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
Right. In 2.10 the ldiskfs inode size was increased from 512 bytes to 1024 bytes in order to fit the more complex PFL layouts. That increased the total amount of space per inode from 2048 bytes to 2560 bytes. I guess the manual needs to be updated.
Principal Lustre Architect
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