[Gluster-users] why i have a good write iops and poor read iops with more stripes?

[Brian Foster]

On 11/07/2012 09:06 PM, 肖力 wrote:
> Hi ,I have 4 dell 2970 server , three server  harddisk is 146Gx6 ,one hard disk is 72Gx6:
> 
> I Want to test different stripe iops, and i test result is :
> 
> ----------------------------------------------------------------------
> 
> no stripe 
> 
> gluster volume create test-volume   transport tcp \
> 172.16.20.231:/exp2  \
> 172.16.20.232:/exp2 \
> 172.16.20.233:/exp2  \
> 
> 4k 100 % random write  288
> 
> 4k 100 % random read  264
> 
> ----------------------------------------------------------------------
> 
> 2 stripe
> 
> gluster volume create test-volume   transport tcp \
> 172.16.20.231:/exp2  \
> 172.16.20.232:/exp2 \
> 172.16.20.233:/exp2  \
> 

This looks the same as the "no stripe" case. Given your numbers differ,
I presume a copy/paste error?

> 4k 100 % random write  439
> 
> 4k 100 % random read  241
> 
> 
> ----------------------------------------------------------------------
> 
> 6 stripe
> 
> gluster volume create test-volume3 stripe 6 transport tcp \
> 172.16.20.231:/exp5 172.16.20.231:/exp6 \
> 172.16.20.232:/exp5 172.16.20.232:/exp6 \
> 172.16.20.233:/exp5 172.16.20.233:/exp6 \
> 

Are you adding bricks on the same spindle(s) here? For example, are
172.16.20.231:/exp{5,6} on the same set of drives? If so, the extra
bricks might not be buying you anything.

> 4k 100 % random write  683
> 
> 4k 100 % random read  151
> 
> ----------------------------------------------------------------------
> 
> My question is why more stripes more write good iops and more poor read iops?
> 

I don't have a specific answer, but I ran a few similar random read
tests to remind myself of the behavior here. One thing our performance
guys have pointed out is that you'll want to run multiple threads
against a gluster native client to maximize iops. Perhaps you're doing
that, but you haven't provided much detail about the actual test you're
running.

Along with that, there is a known bottleneck in the client that is
alleviated by using the 'gid-timeout' mount option (i.e., -o
gid-timeout=1').

Brian

> thks
> 
> xiao li
> 
> 
> 
> 
> 
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