Re: server mode and verify_dump

[Jens Axboe <axboe@kernel.dk>]

On 08/14/2015 01:11 PM, Sitsofe Wheeler wrote:
> On 14 August 2015 at 16:58, Jens Axboe <axboe@kernel.dk> wrote:
>> On 08/14/2015 09:47 AM, Jens Axboe wrote:
>>>
>>> On 08/03/2015 03:12 PM, Sitsofe Wheeler wrote:
>>>>
>>>> Hi,
>>>>
>>>> I've noticed that when running fio in server mode it's not possible to
>>>> get a dump of using verify_dump when a verify mismatch occurs. Is it
>>>> possible to add a mode where the server process saves the mismatch
>>>> files to its current working directory for inspection later?
>>>
>>>
>>> That sounds like an oversight. To save time, can you let me know how you
>>> are invoking fio and with what job file? Should not be that hard to
>>> fixup, it should just work.
>>
>>
>> Just tested this, and the fio backend does dump the files if verify_dump=1
>> is set:
>>
>> [...]
>> <lenny> write3: (g=0): rw=randread, bs=4K-4K/4K-4K/4K-4K, ioengine=sync,
>> iodepth=1
>> <lenny> Starting 1 process
>> <lenny> crc16: verify failed at file file offset 2023424, length 4096
>> <lenny>        Expected CRC: 5b54
>> <lenny>        Received CRC: c1aa
>> <lenny>        received data dumped as file.2023424.received
>> <lenny>        expected data dumped as file.2023424.expected
>
> You're absolutely right. I think I got fooled because of two things:
> 1. I was trying to use dd to stomp zeros while also using the sync
> ioengine on a file in /dev/shm and just getting a file I/O error.
> 2. If fio encounters an error while trying to read the header (even if
> the blocks are all of the same size) it doesn't dump anything at all
> (even in non-server circumstances)...

Right, I suspected that might have been the case. If the header isn't 
valid, then fio doesn't dump any contents. One could argue that it would 
be cleaner if the backend send the files to the frontend to store, since 
that's where you are running fio from. But at least they are there, on 
the backend side.

-- 
Jens Axboe