Re: Urgent problem while using Fio to test random write performance

[Jens Axboe <axboe@kernel.dk>]

On 05/21/2015 02:39 PM, Sitsofe Wheeler wrote:
> On 21 May 2015 at 15:22, David Nellans <david@nellans.org> wrote:
>> you're randwrite to a raw partition. if you had a filesystem on that
>> partition you were trying to use, then well, your data is gone/corrupted.
>> without a filesystem on it, i'm not sure how you'd think that your disc
>> usage has become "100%" without some xgui widgit warning you, so seems
>> likely you did something you didn't mean to with regards to writing to
>> /dev/sdb1 directly
>>
>> if you use fio on devices/partitions with a filesystem, you need to have it
>> write to files or it will trash your filesystem
>
> It's unlikely but it wasn't mentioned which partition became 100%
> full. You should also make sure that /dev/sdb1 really exists as a
> block device (e.g. via using file) otherwise you'll make/fill a
> standard file called /dev/sdb1 .

That's true, though on modern systems that will fail since /dev is 
mounted on devtmpfs which doesn't support O_DIRECT. In general, 
allow_file_create=0 can be used to turn off file creation if you expect 
to run on block devices. This can avoid problems like this.


-- 
Jens Axboe