[dm-devel] [PATCH RFCv2 10/10] dm-dedup: documentation

[Vasily Tarasov]

On Fri, Jan 30, 2015 at 1:55 PM, Vivek Goyal <vgoyal at redhat.com> wrote:
> On Thu, Aug 28, 2014 at 06:16:50PM -0400, Vasily Tarasov wrote:
>
> [..]
>> +Example
>> +=======
>> +
>> +Decide on metadata and data devices:
>> +   # META_DEV=/dev/sdX
>> +   # DATA_DEV=/dev/sdY
>> +
>> +Compute target size assuming 1.5 dedup ratio:
>> +   # DATA_DEV_SIZE=`blockdev --getsz $DATA_DEV`
>> +   # TARGET_SIZE=`expr $DATA_DEV_SIZE \* 10 / 15`
>
> Is above correct? With dm dedupe ratio of 1.5, target size
> should be (15/10) * DATA_DEV_SIZE and not vice-a-versa?
>

You're right, that's a misprint, fixed it.

>> +
>> +Reset metadata device:
>> +   # dd if=/dev/zero of=$META_DEV bs=4096 count=1
>> +
>> +Setup a target:
>> +     echo "0 $TARGET_SIZE dedup $META_DEV $DATA_DEV 4096 md5 cowbtree 100" |\
>> +                             dmsetup create mydedup
>> +
>
> I setup a target and did "dmsetup table" and "dmsetup status" and they
> both seem to be outputting same thing. I think output of "dmsetup table"
> is wrong. As per the man page of dmsetup, you are supposed to output
> the table in a format which can be directly feedback into tagrget for
> loading.
>
> #dmsetup table
> testdedup: 0 2930287752 dedup 244190646 244190646 0 0 4096 8:32 8:48 0 0
> 0 0 0 0
>
> #dmsetup status
> testdedup: 0 2930287752 dedup 244190646 244190646 0 0 4096 8:32 8:48 0 0
> 0 0 0 0
>

Interesting, I actually didn't know that "dmsetup table" output should
be in a format suitable for "dmsetup create/load". Will fix this!

Thanks,
Vasily