Re: New experimental btrfs branch ready for testing

Chris Mason
2009-06-06T00:20:21Z

On Fri, Jun 05, 2009 at 04:27:55PM -0500, Steven Pratt wrote:
> Steven Pratt wrote:
>> Chris Mason wrote:
>>> On Thu, Jun 04, 2009 at 02:02:20PM -0500, Steven Pratt wrote:
>>>
>>>> Chris Mason wrote:
>>>>
>>>>> Hello everyone,
>>>>>
>>>>> Yan Zheng has been doing some major surgery to the back references and
>>>>> extent allocation code, tackling bottlenecks in the code that tracks
>>>>> extents. It scales better with many snapshots and performs better in
>>>>> the common case of no snapshots at all.
>>>>>
>>>>> THE NEW CODE IS A FORWARD ROLLING DISK FORMAT CHANGE. This means
>>>>> it is
>>>>> compatible with the current btrfs disk format, but once you mount a
>>>>> filesystem with the new code, it WILL NO LONGER BE MOUNTABLE FROM OLD
>>>>> KERNELS. Old kernels spit out an error message when you try them
>>>>> on new
>>>>> format filesystems.
>>>>>
>>>>> This is a large change, and I'm hoping to have it stable in time
>>>>> for the
>>>>> 2.6.31 merge window. I've been testing it for about a week now, and
>>>>> haven't been able to cause major problems yet. But, testing the
>>>>> compatibility with old format filesystems is the hard part, and
>>>>> everyone that pulls the new code should backup their data first.
>>>>>
>>>>> I've setup git branches called newformat where you can pull the
>>>>> new code.
>>>>>
>>>>> For the kernel (based on 2.6.30-rc7):
>>>>>
>>>>> git pull
>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable.git
>>>>> newformat
>>>>>
>>>>>
>>>> So I started the performance runs on this. The base tests completed
>>>> fine on the raid system and I will post results as soon as I can
>>>> finish postprocessing, but when I tried to do nodatacow that
>>>> machine it crashed pretty early. Here is console log:
>>>>
>>>
>>> Hi Steve,
>>>
>>> Thanks again for hammering on these. Yan Zheng and I have both been
>>> trying to reproduce problems with nodatacow and with the database random
>>> write run.
>>>
>> So now that the raid machine is actually up, I discovered it got
>> further than I thought on nodatacow. It did all the read tests, but
>> appeared to died on 16 thread random write(not odirect). There were no
>> messages logged to var/log/messages at all. Last I saw was :
>>
>> Jun 4 03:14:24 btrfs1 kernel: [65856.065491] btrfs: setting nodatacow
>> Jun 4 15:24:45 btrfs1 syslogd 1.4.1: restart.
>>
>> Just dead until we rebooted machine later that day.
>
> So the raid system complete the re-run of the nodatacow runs without
> error. So still no idea what happened on this box the first time
> around. As for the single disk system, it died during the random write
> test again, but it now looks like we might have a real HW failure. This
> time we see SCSI error messages. I have replaced the test disks and
> will try one more time.
>
> The net is, I would hold off digging too much into this as even I don't
> have any repeatable errors.

Thanks for rerunning all of this, appreciate the update.

-chris