Re: RBD+KVM problems with sequential read

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> I'm sorry, but I did not understand you :)

Sorry (-: My finger touched the RETURN-key to fast...

Try to setup a bigger value for the read ahead cache, maybe 256 MB?

echo "262144">/sys/block/vda/queue/read_ahead_kb

 

Try also "fio" performance tool - it will show more detailed information.

               [global]

                ioengine=libaio

                invalidate=1

                ramp_time=5

                #exec_prerun="echo 3 > /proc/sys/vm/drop_caches"

                iodepth=16

                runtime=30

                time_based

                direct=1

                bs=1m

                filename=/dev/vda

 

                [seq-write]

                stonewall

                rw=write

 

                [seq-read]

                stonewall

                rw=read

 

Compare the fio result with a fio-test agains the mounted rbd-volume (filename=/dev/rbdX) on your KVM phy. host (not inside the vm).

 

Try this also:

echo 3 > /proc/sys/vm/drop_caches

 

best regards

Danny

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