Lustre 1.6 Operations Manual

23.4.1 Determine the Lustre UUID of an OST
To determine the Lustre UUID of an obdfilter disk (for example, if you mix up the
cables on your OST devices or the SCSI bus numbering suddenly changes and the
SCSI devices get new names), use debugfs to get the last_rcvd file.
23.4.2 Tcpdump
Lustre provides a modified version of tcpdump which helps to decode the complete
Lustre message packet. This tool has more support to read packets from clients to
OSTs, than to decode packets between clients and MDSs. The tcpdump module is
available from Lustre CVS at www.sourceforge.net.
It can be checked out as:
cvs co -d :ext:@cvs.lustre.org:/cvsroot/lustre tcpdump
23.5 Ptlrpc Request History
Each service always maintains request history, which is useful for first occurrence
troubleshooting. Ptlrpc history works as follows:
1. Request_in_callback() adds the new request to the service's request history.
2. When a request buffer becomes idle, add it to the service's request buffer
history list.
3. Cull buffers from the service's request buffer history if it has grown above
"req_buffer_history_max" and remove its reqs from the service's request history.
Request history is accessed/controlled via the following /proc files under the
service directory.
■ req_buffer_history_len
Number of request buffers currently in the history
■ req_buffer_history_max
Maximum number of request buffers to keep
■ req_history
The request history
23-14 Lustre 1.6 Operations Manual • September 2008