Hi Xiaoxi and Zheng,
We've played with both of these some internally, but not for a
production deployment. Mostly just for diagnosing performance problems.
It's been a while since I last played with this, but I hadn't seen a
whole lot of performance improvements at the time. That may have been
due to the hardware in use, or perhaps other parts of Ceph have improved
to the point where this matters now!
On a side note, Btrfs also had a google summer of code project to let
you put metadata on an external device. Originally I think that was
supposed to make it into 3.7, but am not sure if that happened.
Mark
On 01/12/2013 06:21 AM, Yan, Zheng wrote:
On Sat, Jan 12, 2013 at 2:57 PM, Chen, Xiaoxi <xiaoxi.c...@intel.com> wrote:
Hi list,
For a rbd write request, Ceph need to do 3 writes:
2013-01-10 13:10:15.539967 7f52f516c700 10 filestore(/data/osd.21)
_do_transaction on 0x327d790
2013-01-10 13:10:15.539979 7f52f516c700 15 filestore(/data/osd.21) write
meta/516b801c/pglog_2.1a/0//-1 36015~147
2013-01-10 13:10:15.540016 7f52f516c700 15 filestore(/data/osd.21) path:
/data/osd.21/current/meta/DIR_C/pglog\u2.1a__0_516B801C__none
2013-01-10 13:10:15.540164 7f52f516c700 15 filestore(/data/osd.21) write
meta/28d2f4a8/pginfo_2.1a/0//-1 0~496
2013-01-10 13:10:15.540189 7f52f516c700 15 filestore(/data/osd.21) path:
/data/osd.21/current/meta/DIR_8/pginfo\u2.1a__0_28D2F4A8__none
2013-01-10 13:10:15.540217 7f52f516c700 10 filestore(/data/osd.21)
_do_transaction on 0x327d708
2013-01-10 13:10:15.540222 7f52f516c700 15 filestore(/data/osd.21) write
2.1a_head/8abf341a/rb.0.106e.6b8b4567.0000000002d3/head//2 3227648~524288
2013-01-10 13:10:15.540245 7f52f516c700 15 filestore(/data/osd.21) path:
/data/osd.21/current/2.1a_head/rb.0.106e.6b8b4567.0000000002d3__head_8ABF341A__2
l
If using XFS as backend file system and running xfs on top of
traditional sata disk, it will introduce a lot of seeks and therefore reduce
bandwidth, a blktrace is available here :(
http://ww3.sinaimg.cn/mw690/6e1aee47jw1e0qsbxbvddj.jpg) to demonstrate this
issue.( single client running dd on top of a new RBD volumes).
Then I tried to move /osd.X/current/meta to a separate disk, the
bandwidth boosted.(look blktrace at
http://ww4.sinaimg.cn/mw690/6e1aee47jw1e0qsadz1bij.jpg).
I haven't test other access pattern or something else, but it looks to
me that moving such meta to a separate disk (ssd or sata with btrfs) will
benefit ceph write performance, is it true? Will ceph introduce this feature in
the future? Is there any potential problem for such hack?
Did you try putting XFS metadata log a separate and fast device
(mkfs.xfs -l logdev=/dev/sdbx,size=10000b). I think it will boost
performance too.
Regards
Yan, Zheng
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
