You may want to set "ioengine=rbd", I guess.

Cheers,

----- Original Message -----
From: "min fang" <louisfang2...@gmail.com>
To: "ceph-users" <ceph-users@lists.ceph.com>
Sent: Tuesday, March 1, 2016 1:28:54 PM
Subject: [ceph-users]  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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