On 8/21/2012 9:51 AM, Miquel van Smoorenburg wrote:
> On 08/20/2012 01:34 AM, Stan Hoeppner wrote:
>> I'm glad you jumped in David. You made a critical statement of fact
>> below which clears some things up. If you had stated it early on,
>> before Miquel stole the thread and moved it to LKML pro
On 08/20/2012 01:34 AM, Stan Hoeppner wrote:
I'm glad you jumped in David. You made a critical statement of fact
below which clears some things up. If you had stated it early on,
before Miquel stole the thread and moved it to LKML proper, it would
have short circuited a lot of this discussion.
On 20/08/2012 02:01, NeilBrown wrote:
On Sun, 19 Aug 2012 18:34:28 -0500 Stan Hoeppner
wrote:
Since we are trying to set the record straight
md/RAID6 must read all devices in a RMW cycle.
md/RAID6 must read all data devices (i.e. not parity devices) which it is not
going to write to, i
On Sun, 19 Aug 2012 18:34:28 -0500 Stan Hoeppner
wrote:
> On 8/19/2012 9:01 AM, David Brown wrote:
> > I'm sort of jumping in to this thread, so my apologies if I repeat
> > things other people have said already.
>
> I'm glad you jumped in David. You made a critical statement of fact
> below wh
On 8/19/2012 9:01 AM, David Brown wrote:
> I'm sort of jumping in to this thread, so my apologies if I repeat
> things other people have said already.
I'm glad you jumped in David. You made a critical statement of fact
below which clears some things up. If you had stated it early on,
before Miqu
On 08/17/2012 09:31 AM, Stan Hoeppner wrote:
On 8/16/2012 4:50 PM, Miquel van Smoorenburg wrote:
I did a simple test:
* created a 1G partition on 3 seperate disks
* created a md raid5 array with 512K chunksize:
mdadm -C /dev/md0 -l 5 -c $((1024*512)) -n 3 /dev/sdb1 /dev/sdc1
/dev/sdd1
* ran
On 8/16/2012 4:50 PM, Miquel van Smoorenburg wrote:
> On 16-08-12 1:05 PM, Stan Hoeppner wrote:
>> On 8/15/2012 6:07 PM, Miquel van Smoorenburg wrote:
>>> Ehrm no. If you modify, say, a 4K block on a RAID5 array, you just have
>>> to read that 4K block, and the corresponding 4K block on the
>>> par
On 16-08-12 1:05 PM, Stan Hoeppner wrote:
On 8/15/2012 6:07 PM, Miquel van Smoorenburg wrote:
Ehrm no. If you modify, say, a 4K block on a RAID5 array, you just have
to read that 4K block, and the corresponding 4K block on the
parity drive, recalculate parity, and write back 4K of data and 4K
of
On 8/15/2012 6:07 PM, Miquel van Smoorenburg wrote:
> In article you write:
>> It's time to blow away the array and start over. You're already
>> misaligned, and a 512KB chunk is insanely unsuitable for parity RAID,
>> but for a handful of niche all streaming workloads with little/no
>> rewrite,
On Wed, 15 Aug 2012 18:50:44 -0500
Stan Hoeppner wrote:
> TTBOMK there are two, and only two, COW filesystems in existence: ZFS and
> BTRFS.
There is also NILFS2: http://www.nilfs.org/en/
And in general, any https://en.wikipedia.org/wiki/Log-structured_file_system
is COW by design, but afaik o
On Wed, Aug 15, 2012 at 4:50 PM, Stan Hoeppner wrote:
> On 8/15/2012 5:10 PM, Andy Lutomirski wrote:
>> On Wed, Aug 15, 2012 at 3:00 PM, Stan Hoeppner
>> wrote:
>>> On 8/15/2012 12:57 PM, Andy Lutomirski wrote:
On Wed, Aug 15, 2012 at 4:50 AM, John Robinson
wrote:
> On 15/08/2012
On 8/15/2012 5:10 PM, Andy Lutomirski wrote:
> On Wed, Aug 15, 2012 at 3:00 PM, Stan Hoeppner wrote:
>> On 8/15/2012 12:57 PM, Andy Lutomirski wrote:
>>> On Wed, Aug 15, 2012 at 4:50 AM, John Robinson
>>> wrote:
On 15/08/2012 01:49, Andy Lutomirski wrote:
>
> If I do:
> # dd if=/
In article you write:
>It's time to blow away the array and start over. You're already
>misaligned, and a 512KB chunk is insanely unsuitable for parity RAID,
>but for a handful of niche all streaming workloads with little/no
>rewrite, such as video surveillance or DVR workloads.
>
>Yes, 512KB is
On Wed, Aug 15, 2012 at 3:00 PM, Stan Hoeppner wrote:
> On 8/15/2012 12:57 PM, Andy Lutomirski wrote:
>> On Wed, Aug 15, 2012 at 4:50 AM, John Robinson
>> wrote:
>>> On 15/08/2012 01:49, Andy Lutomirski wrote:
If I do:
# dd if=/dev/zero of=/dev/md0p1 bs=8M
>>>
>>> [...]
>>>
It
On 8/15/2012 12:57 PM, Andy Lutomirski wrote:
> On Wed, Aug 15, 2012 at 4:50 AM, John Robinson
> wrote:
>> On 15/08/2012 01:49, Andy Lutomirski wrote:
>>>
>>> If I do:
>>> # dd if=/dev/zero of=/dev/md0p1 bs=8M
>>
>> [...]
>>
>>> It looks like md isn't recognizing that I'm writing whole stripes whe
On Wed, Aug 15, 2012 at 4:50 AM, John Robinson
wrote:
> On 15/08/2012 01:49, Andy Lutomirski wrote:
>>
>> If I do:
>> # dd if=/dev/zero of=/dev/md0p1 bs=8M
>
> [...]
>
>> It looks like md isn't recognizing that I'm writing whole stripes when
>> I'm in O_DIRECT mode.
>
>
> I see your md device is p
On 15/08/2012 01:49, Andy Lutomirski wrote:
If I do:
# dd if=/dev/zero of=/dev/md0p1 bs=8M
[...]
It looks like md isn't recognizing that I'm writing whole stripes when
I'm in O_DIRECT mode.
I see your md device is partitioned. Is the partition itself stripe-aligned?
Cheers,
John.
--
To uns
On 2012-08-15 09:12 Andy Lutomirski Wrote:
>Ubuntu's 3.2.0-27-generic. I can test on a newer kernel tomorrow.
I guess maybe miss the blk_plug function.
Can you add this patch and retest.
Move unplugging for direct I/O from around ->direct_IO() down to
do_blockdev_direct_IO(). This implicitly add
Ubuntu's 3.2.0-27-generic. I can test on a newer kernel tomorrow.
--Andy
On Tue, Aug 14, 2012 at 6:07 PM, kedacomkernel wrote:
> On 2012-08-15 08:49 Andy Lutomirski Wrote:
>>If I do:
>># dd if=/dev/zero of=/dev/md0p1 bs=8M
>>then iostat -m 5 says:
>>
>>avg-cpu: %user %nice %system %iowait
On 2012-08-15 08:49 Andy Lutomirski Wrote:
>If I do:
># dd if=/dev/zero of=/dev/md0p1 bs=8M
>then iostat -m 5 says:
>
>avg-cpu: %user %nice %system %iowait %steal %idle
> 0.000.00 26.88 35.270.00 37.85
>
>Device:tpsMB_read/sMB_wrtn/sMB_read
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