Description of problem: vmstat -d <delay> <count> shows activity on disks when there is none. These disk are attached to Data Direct S2A9500 controllers. The quiesced state of the disks has been verified via ddns stats command on the controllers, and via a sar -d run during the same interval. Version-Release number of selected component (if applicable): This is RHEL 4 WS x86_64 using procps-3.2.3-8.3 How reproducible: This has been reproduced on every node that I have tried it on. Just run vmstat -d 5 5, while verifying no disk activity via the ddn controllers, or sar -d 5 5. Relevant output attached. /dev/sda is the only sd device that should show activity. Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
Created attachment 132601 [details] output from vmstat -d and sar -d over the same time interval.
The source data for vmstat is /proc/diskstats. You can try check this file if you think that vmstat outputs unreliable information. The /proc/diskstats is I/O statistics (history) -- so these numbers mean that there was an activity, but it says nothing about actual activity. You need to check (compare) statistics from more loops. I don't see any progress for sdb I/O activity in your output, I see changes for sda only: sda 28188 7509 1006241 123646 80442 99410 1438784 1917445 0 131 sdb 4841 1669 35064 19417 219011 19747547 50370193 1356765620 0 267 sda 28188 7509 1006241 123646 80447 99429 1438976 1917447 0 131 sdb 4841 1669 35064 19417 219011 19747547 50370193 1356765620 0 267 sda 28188 7509 1006241 123646 80451 99435 1439056 1917448 0 131 sdb 4841 1669 35064 19417 219011 19747547 50370193 1356765620 0 267 Is it more clear now?
Nobody responded to this for almost a year... Closing.