Lustre 1.6 Operations Manual

25.5 Performing Direct I/O
Starting with 1.4.7, Lustre supports the O_DIRECT flag to open.
Applications using the read() and write() calls must supply buffers aligned on a page
boundary (usually 4 K). If the alignment is not correct, the call returns -EINVAL.
Direct I/O may help performance in cases where the client is doing a large amount
of I/O and is CPU-bound (CPU utilization 100%).
25.5.1 Making Filesystem Objects Immutable
An immutable file or directory is one that cannot be modified, renamed or removed.
To do this:
chattr +i
To remove this flag, use chattr –i
25-10 Lustre 1.6 Operations Manual • September 2008