Question

7

Investigate disk writes further to find out which process writes to my SSD

rated 0 times [ 7] [ 0] / answers: 1 / hits: 12806 / 1 Year ago, mon, may 15, 2023, 4:04:13

I try to minimize disk writes to my new SSD system drive.
I'm stuck with iostat output:

~ > iostat -d 10 /dev/sdb

Linux 2.6.32-44-generic (Pluto)     13.11.2012  _i686_  (2 CPU)



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               8,60       212,67       119,45   21010156   11800488



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               3,00         0,00        40,00          0        400



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               1,70         0,00        18,40          0        184



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               1,20         0,00        28,80          0        288



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               2,20         0,00        32,80          0        328



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               1,20         0,00        23,20          0        232



Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn

sdb               3,40        19,20        42,40        192        424

As I see there are writes to sdb. How can I resolve which process writes?

I know about iotop, but it doesn't show which filesystem is being accessed.

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answered 1 Year ago memorrappin · Accepted Answer

The following uses the kernel's virtual memory block dump mechanism. First get the perl script:

wget https://raw.githubusercontent.com/true/aspersa-mirror/master/iodump

Then turn on block dump:

echo 1 | sudo tee /proc/sys/vm/block_dump

And run the following:

while true; do sleep 1; sudo dmesg -c; done  | perl iodump

..and press Controlc to finish, you will see something like the following:

^C# Caught SIGINT.

TASK                   PID      TOTAL       READ      WRITE      DIRTY DEVICES

jbd2/sda3-8            620         40          0         40          0 sda3

jbd2/sda1-8            323         21          0         21          0 sda1

#1                    4746         11          0         11          0 sda3

flush-8:0             2759          7          0          7          0 sda1, sda3

command-not-fou       9703          4          4          0          0 sda1

mpegaudioparse8       8167          2          2          0          0 sda3

bash                  9704          1          1          0          0 sda1

bash                  9489          1          0          1          0 sda3

mount.ecryptfs_       9698          1          1          0          0 sda1

And turn off block dump when you are finished:

echo 0 | sudo tee /proc/sys/vm/block_dump

Thanks to http://www.xaprb.com/blog/2009/08/23/how-to-find-per-process-io-statistics-on-linux/ for this helpful info.