Re: Does fio write only 0x00s?

[Troels Arvin <troels@arvin.dk>]

Hello,

On Mar 15, Jens Axboe wrote:
> By default, fio will at init time randomly fill the buffer of the
> allocated IO units. If you are using the sync io engine, then only one
> buffer will be allocated and that will be repeatedly written. So yes,
> that'll compress very nicely.

I'm using libaio. So the data from that shouldn't compress all that much?


> You can enable refill_buffers=1 and
> that'll cause fio to randomly fill it everytime it's submitted instead.
> That should effectively disable compression at the storage end.

Turning refill_buffers on or off doesn't seem to make much of a 
difference when compressing fil's work-file with "gzip -2" (201MB vs 
198MB). But perhaps, "gzip -2" still compreses more than one can expect 
from a storage system?

I'm probably missing something. Here's the job description file I'm 
using (in this case only testing a small amount of I/O; when I was 
testing the storage systems, I used size=10g and six numjobs=6):
===========================================================
[global]
description=Emulation of Intel IOmeter File Server Access Pattern

[iometer]
bssplit=512/10:1k/5:2k/5:4k/60:8k/2:16k/4:32k/4:64k/10
rw=randrw
rwmixread=70
direct=1
size=1g
ioengine=libaio
iodepth=256
refill_buffers=0
===========================================================

-- 
Regards,
Troels Arvin <troels@arvin.dk>
http://troels.arvin.dk/