If you are mapping the RBD with the kernel driver then you're not using librbd so these settings will have no effect I believe. The kernel driver does its own caching but I don't believe there are any settings to change its default behavior.
On Mon, Feb 29, 2016 at 9:36 PM, Shinobu Kinjo <skinjo@xxxxxxxxxx> wrote:
You may want to set "ioengine=rbd", I guess.
Cheers,
_______________________________________________
----- Original Message -----
From: "min fang" <louisfang2013@xxxxxxxxx>
To: "ceph-users" <ceph-users@xxxxxxxxxxxxxx>
Sent: Tuesday, March 1, 2016 1:28:54 PM
Subject: rbd cache did not help improve performance
Hi, I set the following parameters in ceph.conf
[client]
rbd cache=true
rbd cache size= 25769803776
rbd readahead disable after byte=0
map a rbd image to a rbd device then run fio testing on 4k read as the command
./fio -filename=/dev/rbd4 -direct=1 -iodepth 64 -thread -rw=read -ioengine=aio -bs=4K -size=500G -numjobs=32 -runtime=300 -group_reporting -name=mytest2
Compared the result with setting rbd cache=false and enable cache model, I did not see performance improved by librbd cache.
Is my setting not right, or it is true that ceph librbd cache will not have benefit on 4k seq read?
thanks.
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