On 9 March 2016 at 16:43, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote:
> On Wed, Mar 9, 2016 at 2:36 PM, Roman Mamedov <rm@xxxxxxxxxxx> wrote:
>> On Wed, 9 Mar 2016 15:25:19 -0500
> This is a better qualification than my answer.
>
>>
>> Now if you want to do some more performance evaluation, check with your dstat
>> if both disks happen to *write* data in parallel, when you write to the array,
>> as ideally they should. Last I checked they mostly didn't, and this almost
>> halved write performance on a Btrfs RAID1 compared to a single disk.
>
> I've found it to be about the same or slightly less than single disk.
> But most of my writes to raid1 are btrfs receive.
Here are my results for sending pv /tmpfs_mem_disk/deleteme.tar -pabet
> /scratch/deleteme.tar, after I've cleared all caches. Pv states the
average rate was 77MiB/s, which seems low for a 4GB file. Here is the
dstat section for peak rates for writing.
----system---- -dsk/total----dsk/sdb-----dsk/sdd--
time | read writ: read writ: read writ
09-03 16:48:43| 48k 145M: 0 74M: 48k 72M
09-03 16:48:44| 0 120M: 0 74M: 0 46M
09-03 16:48:45| 840k 144M: 0 74M: 0 70M
09-03 16:48:46| 0 147M: 0 80M: 0 67M
and for reading many >200MB raw WAVs from one subvolume while writing
a ~20GB tar to another subvolume:
09-03 16:59:57| 56M 103M: 0 54M: 56M 50M
09-03 16:59:58| 48M 118M: 32k 56M: 48M 62M
09-03 16:59:59| 54M 113M: 0 57M: 54M 55M
09-03 17:00:00| 43M 116M: 0 54M: 43M 63M
09-03 17:00:01| 60M 118M: 0 64M: 60M 54M
09-03 17:00:02| 57M 97M: 32k 48M: 54M 49M
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