Re: Simulating faulty disk

Yathindra
2011-10-20T15:59:23Z

Thanks so much Bryn. Appreciate it.

On 10/20/2011 9:56 AM, Bryn M. Reeves wrote:
> On 10/20/2011 04:45 PM, Yathindra wrote:
>> Hi Bryn,
>>
>> Thanks for that info. Could you please tell me where I can find more
>> details about using it.
>>
>> Thanks again,
>> Yathi
>
> There's a couple of brief files describing the targets in the
> Documentation/device-mapper directory:
>
> http://www.kernel.org/doc/Documentation/device-mapper/dm-flakey.txt
> http://www.kernel.org/doc/Documentation/device-mapper/delay.txt
>
> They both work like the linear target (except that they introduce the
> specified faults according to their parameters).
>
> To set up a device with both you'd need to use a pair of stacked
> devices so something like:
>
> dmsetup create d0 --table="0 $SECTORS delay $DEVICE 0 500"
> dmsetup create f0 --table="0 $SECTORS flakey /dev/mapper/d0 0 9 1"
>
> This will create a device /dev/mapper/f0 that is drops out for 1s in
> every 10 and has a 500ms delay on reads and writes. SECTORS is the
> size of the underlying device in sectors (use e.g. $(blockdev
> --getsize)).
>
> You can optionally specify separate delays/device for writes to the
> delay layer and write loss / write corruption for the flakey layer -
> see the doc files and also the comments above flakey_ctr and delay_ctr
> for more details.
>
> Regards,
> Bryn.