Lustre 1.6 Operations Manual

19.2.1 sgpdd_survey
Use the sgpdd_survey tool to test bare metal performance, while bypassing as
much of the kernel as possible. This script requires the sgp_dd package, although it
does not require Lustre software. This survey may be used to characterize the
performance of a SCSI device by simulating an OST serving multiple stripe files. The
data gathered by this survey can help set expectations for the performance of a
Lustre OST exporting the device.
The script uses sgp_dd to carry out raw sequential disk I/O. It runs with variable
numbers of sgp_dd threads to show how performance varies with different request
queue depths.
The script spawns variable numbers of sgp_dd instances, each reading or writing a
separate area of the disk to demonstrate performance variance within a number of
concurrent stripe files.
The device(s) used must meet one of the two tests described below:
SCSI device:
Must appear in the output of sg_map (make sure the kernel module "sg" is loaded)
Raw device:
Must appear in the output of raw -qa
If you need to create raw devices in order to use the sgpdd_survey tool, note that
raw device 0 cannot be used due to a bug in certain versions of the "raw" utility
(including that shipped with RHEL4U4.)
You may not mix raw and SCSI devices in the test specification.
Caution – The sgpdd_survey script overwrites the device being tested, which
results in the LOSS OF ALL DATA on that device. Exercise caution when selecting
the device to be tested.
Chapter 19 Lustre I/O Kit 19-3