* [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
@ 2012-02-21 16:29 Ray Morris
2012-02-21 16:50 ` Alasdair G Kergon
2012-02-21 17:01 ` Les Mikesell
0 siblings, 2 replies; 6+ messages in thread
From: Ray Morris @ 2012-02-21 16:29 UTC (permalink / raw)
To: LVM general discussion and development
Moving several terabytes of data, I was again struck by the very
large difference in performance between copying data in small chunks
for large chunks. After seeing larger block sizes make dd eight times
faster, I tried increasing mirror_region_size in lvm.conf:
pvmove with default mirror_region_size of 512: ~4-6 MB/s
pvmove with increased mirror_region_size of 4096: ~22-32 MB/s
Although this was somewhat unscientific testing, I'm quite curious
what results others get on their hardware. The effect was most
pronounced for me on a system with a 9550SX-12. I'll do some testing
on a 8888ELP next week.
If 4096 is OFTEN several times faster than 512, would it make sense
to consider canging the default?
--
Ray Morris
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
2012-02-21 16:29 [linux-lvm] mirror_region_size default: 4096 six times faster than 512? Ray Morris
@ 2012-02-21 16:50 ` Alasdair G Kergon
2012-02-21 17:01 ` Les Mikesell
1 sibling, 0 replies; 6+ messages in thread
From: Alasdair G Kergon @ 2012-02-21 16:50 UTC (permalink / raw)
To: LVM general discussion and development
On Tue, Feb 21, 2012 at 10:29:32AM -0600, Ray Morris wrote:
> If 4096 is OFTEN several times faster than 512, would it make sense
> to consider canging the default?
Hard to know, really.
What could be useful though would be some tuning scripts, that run tests like
that on a given installation and suggest tweaks like that.
Alasdair
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
2012-02-21 16:29 [linux-lvm] mirror_region_size default: 4096 six times faster than 512? Ray Morris
2012-02-21 16:50 ` Alasdair G Kergon
@ 2012-02-21 17:01 ` Les Mikesell
2012-02-23 16:46 ` Ray Morris
1 sibling, 1 reply; 6+ messages in thread
From: Les Mikesell @ 2012-02-21 17:01 UTC (permalink / raw)
To: LVM general discussion and development
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On Tue, Feb 21, 2012 at 10:29 AM, Ray Morris <support@bettercgi.com> wrote:
>
> If 4096 is OFTEN several times faster than 512, would it make sense
> to consider canging the default?
>
What disks are underneath this? One of the new 4k sector types?
--
Les Mikesell
lesmikesell@gmail.com
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
2012-02-21 17:01 ` Les Mikesell
@ 2012-02-23 16:46 ` Ray Morris
2012-02-24 15:57 ` Les Mikesell
0 siblings, 1 reply; 6+ messages in thread
From: Ray Morris @ 2012-02-23 16:46 UTC (permalink / raw)
To: LVM general discussion and development
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512 byte sector consumer SATA drives from Seagate and Hitachi. Drives attached to a 9560 RAID card exhibited more difference than drives in a different system attached to the motherboard directly. As I mentioned, I haven't done extensive or highly scientific testing, but in general, across various hardware using various software, copying chinks of a few MBs seems to always beat copying bytes or KB per chunk.
--
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
Les Mikesell <lesmikesell@gmail.com> wrote:
On Tue, Feb 21, 2012 at 10:29 AM, Ray Morris <support@bettercgi.com> wrote:
If 4096 is OFTEN several times faster than 512, would it make sense
to consider canging the default?
What disks are underneath this? One of the new 4k sector types?
--
Les Mikesell
lesmikesell@gmail.com
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
2012-02-23 16:46 ` Ray Morris
@ 2012-02-24 15:57 ` Les Mikesell
2012-02-27 20:40 ` Ray Morris
0 siblings, 1 reply; 6+ messages in thread
From: Les Mikesell @ 2012-02-24 15:57 UTC (permalink / raw)
To: LVM general discussion and development
On Thu, Feb 23, 2012 at 10:46 AM, Ray Morris <support@bettercgi.com> wrote:
> 512 byte sector consumer SATA drives from Seagate and Hitachi. Drives
> attached to a 9560 RAID card exhibited more difference than drives in a
> different system attached to the motherboard directly. As I mentioned, I
> haven't done extensive or highly scientific testing, but in general, across
> various hardware using various software, copying chinks of a few MBs seems
> to always beat copying bytes or KB per chunk.
What kind of RAID? Anything that involves parity is going to require
small writes to read and merge the new data into blocks and rewrite
the parity.
--
Les Mikesell
lesmikesell@gmail.com
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [linux-lvm] mirror_region_size default: 4096 six times faster than 512?
2012-02-24 15:57 ` Les Mikesell
@ 2012-02-27 20:40 ` Ray Morris
0 siblings, 0 replies; 6+ messages in thread
From: Ray Morris @ 2012-02-27 20:40 UTC (permalink / raw)
To: LVM general discussion and development
> copying chunks of a few MBs seems to always beat copying
> > bytes or KB per chunk.
> What kind of RAID? Anything that involves parity is going to require
> small writes to read and merge the new data into blocks and rewrite
> the parity.
At least mdadm RAID1 and RAID5. Hardware raid5 was slow with 512,
but not yet tested with 4096 or higher. I'll test it in a few days
after a migration completes.
--
Ray Morris
support@bettercgi.com
Strongbox - The next generation in site security:
http://www.bettercgi.com/strongbox/
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On Fri, 24 Feb 2012 09:57:30 -0600
Les Mikesell <lesmikesell@gmail.com> wrote:
> On Thu, Feb 23, 2012 at 10:46 AM, Ray Morris <support@bettercgi.com>
> wrote:
> > 512 byte sector consumer SATA drives from Seagate and Hitachi.
> > Drives attached to a 9560 RAID card exhibited more difference than
> > drives in a different system attached to the motherboard directly.
> > As I mentioned, I haven't done extensive or highly scientific
> > testing, but in general, across various hardware using various
> > software, copying chinks of a few MBs seems to always beat copying
> > bytes or KB per chunk.
>
>
> What kind of RAID? Anything that involves parity is going to require
> small writes to read and merge the new data into blocks and rewrite
> the parity.
>
^ permalink raw reply [flat|nested] 6+ messages in thread
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2012-02-21 16:29 [linux-lvm] mirror_region_size default: 4096 six times faster than 512? Ray Morris
2012-02-21 16:50 ` Alasdair G Kergon
2012-02-21 17:01 ` Les Mikesell
2012-02-23 16:46 ` Ray Morris
2012-02-24 15:57 ` Les Mikesell
2012-02-27 20:40 ` Ray Morris
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