Re: dstat shows unexpected result for two disk RAID1

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grr.  Gmail is terrible :-/

I understood that a btrfs RAID1 would at best grab one block from sdb
and then one block from sdd in round-robin fashion, or at worse grab
one chunk from sdb and then one chunk from sdd.  Alternatively I
thought that it might read from both simultaneously, to make sure that
all data matches, while at the same time providing single-disk
performance.  None of these was the case.  Running a single
IO-intensive process reads from a single drive.

Did I misunderstand the documentation and is this normal, or is this a bug?
Nicholas

On 9 March 2016 at 15:21, Nicholas D Steeves <nsteeves@xxxxxxxxx> wrote:
> Hello everyone,
>
> I've run into an expected behaviour for a my two disk RAID1.  I mount
> with UUIDs, because sometimes my USB disk gets /dev/sdc instead of
> /dev/sdd.  The two elements of my RAID1 are currently sdb and sdd.
>
> dstat -tdD total,sdb,sdc,sdd
>
> It seems that per process, reads come from either sdb or sdd.  This
> surprises me, because I understood that a btrfs RAID1
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