Lustre 1.6 Operations Manual

25.6 Other I/O Options
This section describes other I/O options, including end-to-end client checksums and
striping using ioctl.
25.6.1 End-to-End Client Checksums
To guard against data corruption on the network, a Lustre client can perform end-toend
data checksums. This computes a 32-bit checksum of the data read or written on
both the client and server, and ensures that the data has not been corrupted in transit
over the network. The ldiskfs backing filesystem does NOT do any persistent
checksumming, so it does not detect corruption of data in the OST filesystem.
In Lustre 1.6.5, the checksumming feature is enabled, by default, on individual client
nodes. If the client or OST detects a checksum mismatch, then an error is logged in
the syslog of the form:
LustreError: BAD WRITE CHECKSUM: changed in transit before arrival at
OST: from 192.168.1.1@tcp inum 8991479/2386814769 object 1127239/0
extent [102400-106495]
If this happens, the client will re-read or re-write the affected data up to 5 times to
get a good copy of the data over the network. If it is still not possible, then an I/O
error is returned to the application.
To enable checksums on a client:
echo 1 > /proc/fs/lustre/llite/{fsname}/checksum_pages
To disable checksums on a client:
echo 0 > /proc/fs/lustre/llite/{fsname}/checksum_pages
Chapter 25 Striping and I/O Options 25-11