r=nathan

[fs/lustre-release.git] / lustre-iokit / sgpdd-survey / README

diff --git a/lustre-iokit/sgpdd-survey/README b/lustre-iokit/sgpdd-survey/README
index 78fa376..67dd23b 100644 (file)
--- a/lustre-iokit/sgpdd-survey/README
+++ b/lustre-iokit/sgpdd-survey/README
@@ -1,9 +1,15 @@
+WARNING: Running sgp_dd will ERASE the contents of the disk devices.
+         This is NOT to be run on any OST where you care about any data
+        or you are not expecting to reformat the filesystem afterward.
 
 Requirements
 ------------
 
 . sg3_utils (for sgp_dd)
-. SCSI device
+  SCSI device
+  Or, if using non-scsi disk
+  raw device support
+  sg3_utils
 
 
 Overview
@@ -22,6 +28,13 @@ The script spawns variable numbers of sgp_dd instances, each reading or
 writing a separate area of the disk to show how performance varies with the
 number of concurrent stripe files.
 
+The device(s) used must meet one of two tests:
+SCSI device:
+       Must appear in the output of 'sg_map'
+Raw device:
+       Must appear in the output of 'raw -qa'
+You may not mix raw and SCSI devices in the test specification.
+
 
 Running
 -------