Lustre 1.6 Operations Manual

21.3.3.3 Number of Inodes for OST
For OST filesystems, it is normally advantageous to take local filesystem usage into
account. Try to minimize the number of inodes created on each OST. This helps
reduce the format and e2fsck time, and makes more space available for data.
Presently, Lustre has 1 inode per 16 KB of space in the OST filesystem (by default).
In many environments, this is far too many inodes for the average file size. As a
general guideline, the OSTs should have at least a number of inodes indicated by
this formula:
num_ost_inodes = 4 * * /
To specify the number of inodes on OST filesystems, use the -N
option to --mkfsoptions. Alternately, if you know the average file size, you can
also specify the OST inode count for the OST filesystems using: -i . For example, if the average file size is 16 MB and there
are, by default, 4 stripes per file then --mkfsoptions=-i 1048576 would be
appropriate.)
For more details on formatting MDT and OST filesystems, see Formatting.
21.4 Network Tuning
During IOR runs, especially reads, one or more nodes may become CPU-bound
(which may slow down the remaining nodes and compromise read rates). This issue
is likely related to RX overflow errors on the nodes (caused by an upstream e1000
driver). To resolve this issue, increase the RX ring buffer size (default is 256). Use
either:
■ /sbin/ethtool -G ethX rx 4096
■ e1000 module option 'RxDescriptors=4096'
21.5 DDN Tuning
This section provides guidelines to configure DDN storage arrays for use with
Lustre. For more complete information on DDN tuning, refer to the performance
management section of the DDN manual of your product, available at
http://www.ddnsupport.com/manuals.html.
This section covers the following DDN arrays:
21-6 Lustre 1.6 Operations Manual • September 2008