Re: Does fio write only 0x00s?

[Troels Arvin <troels@arvin.dk>]

Hello,

Den 16-03-2010 09:05, skrev Jens Axboe:
> I think what you are missing is that the random writes will create a
> large sparse file. The Output is 10G, and you are doing a lot of reads.
> So you could end up writing only 30% of the 10G, the rest would be
> sparse holes in the file.

Yes, that part about the file sparseness was I had to grasp.

Expressed in another way: If I filter out the null-bytes from fio's 
work-file (cat iometer.1.0 | tr -d '\0'), then the remainder doesn't 
compress at all using gzip with default options.

So I'll stop worrying about storage-side compression/de-duplication when 
interpreting fio's results.

Thanks.

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