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Feature Request
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Resolution: Unresolved
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Normal
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virtio-blk disks rotational status is seen as '1' from the guest OS (linux). this can be verified like this:
cat /sys/block/vd*/queue/rotational
We are seeing an performance increase of 6% when setting that value to 0 (i.e. non rotational). Especially in the scenario when that disk is in fact a multipath LUN provided by a SAN array.
This is an example of a fio test that provided that result
[global] ioengine=libaio direct=1 runtime=60 time_based=1 group_reporting=1 numjobs=4 ; --- Test 1: Random 4K reads (the ultimate HDD killer) --- [random-4k-read] stonewall rw=randread bs=4k iodepth=32 filename=/tmp/fio-test.dat size=4g new_group ; --- Test 2: Random 4K writes --- [random-4k-write] stonewall rw=randwrite bs=4k iodepth=32 filename=/tmp/fio-test.dat size=4g new_group ; --- Test 3: High queue depth random mixed (70/30 r/w) --- [random-mixed-qd64] stonewall rw=randrw rwmixread=70 bs=4k iodepth=64 filename=/tmp/fio-test.dat size=4g new_group ; --- Test 4: Sequential read (HDDs should be competitive here) --- [seq-read-128k] stonewall rw=read bs=128k iodepth=8 filename=/tmp/fio-test.dat size=4g new_group ; --- Test 5: Sequential write --- [seq-write-128k] stonewall rw=write bs=128k iodepth=8 filename=/tmp/fio-test.dat size=4g
it can be run with this command:
fio --name=setup --filename=/tmp/fio-test.dat --size=4g --rw=write --bs=1m --direct=1
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RHEL-151896 virtio-blk should provide an option to set the disk rotational status
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- New
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- Planning
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