Hi Jim,
The output from bonnie on my boot drive is:
File './Bonnie.27964', size: 0
Writing with putc()...done
Rewriting...done
Writing intelligently...done
Reading with getc()...done
Reading intelligently...done
Seeker 2...Seeker 1...Seeker 3...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input--
--Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %
CPU /sec %CPU
0 36325 98.1 66207 22.9 60663 16.2 50553 99.9 710972
100.0 44659.8 191.3
And the output from the RAID drive is:
File './Bonnie.27978', size: 0
Writing with putc()...done
Rewriting...done
Writing intelligently...done
Reading with getc()...done
Reading intelligently...done
Seeker 1...Seeker 2...Seeker 3...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input--
--Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %
CPU /sec %CPU
0 40365 99.4 211625 61.4 212425 57.0 50740 99.9 730515
100.0 45897.9 190.1
Each drive in the RAID 5 is a 400 GB serial ATA drive. I'm not sure
the manufacturer or the model number as it was all in a packaged box
when we received it and I didn't check.
Do these numbers seem decent enough for a Postgres database?
Thanks,
____________________________________________________________________
Brendan Duddridge | CTO | 403-277-5591 x24 | brendan@xxxxxxxxxxxxxx
ClickSpace Interactive Inc.
Suite L100, 239 - 10th Ave. SE
Calgary, AB T2G 0V9
http://www.clickspace.com
On May 2, 2006, at 3:53 PM, Jim C. Nasby wrote:
BTW, you should be able to check to see what the controller is
actually
doing by pulling one of the drives from a running array. If it only
hammers 2 drives during the rebuild, it's RAID10. If it hammers all
the
drives, it's 0+1.
As for Xserve raid, it is possible to eliminate most (or maybe even
all)
of the overhead associated with RAID5, depending on how tricky the
controller wants to be. I believe many large storage appliances
actually
use RAID5 internally, but they perform a bunch of 'magic' behind the
scenes to get good performance from it. So, it is possible that the
XServe RAID performs quite well on RAID5. If you provided the results
from bonnie as well as info about the drives I suspect someone here
could tell you if you're getting close to RAID10 performance or not.
On Tue, May 02, 2006 at 02:34:16PM -0500, Will Reese wrote:
RAID 10 is better than RAID 0+1. There is a lot of information on
the net about this, but here is the first one that popped up on
google for me.
http://www.pcguide.com/ref/hdd/perf/raid/levels/multLevel01-c.html
The quick summary is that performance is about the same between the
two, but RAID 10 gives better fault tolerance and rebuild
performance. I have seen docs for RAID cards that have confused
these two RAID levels. In addition, some cards claim to support RAID
10, when they actually support RAID 0+1 or even RAID 0+1 with
concatenation (lame, some of the Dell PERCs have this).
RAID 10 with 6 drives would stripe across 3 mirrored pairs. RAID 0+1
with 6 drives is a mirror of two striped arrays (3 disks each). RAID
0+1 (with concatenation) using 6 drives is a mirror of two volumes
(kind of like JBOD) each consisting of 3 drives concatenated together
(it's a cheap implementation, and it gives about the same performance
as RAID 1 but with increased storage capacity and less fault
tolerance). RAID 10 is better than RAID 5 (especially with 6 or less
disks) because you don't have the performance hit for parity (which
dramatically affects rebuild performance and write performance) and
you get better fault tolerance (up to 3 disks can fail in a 6 disk
RAID 10 and you can still be online, with RAID 5 you can only lose 1
drive). All of this comes with a higher cost (more drives and higher
end cards).
-- Will Reese http://blog.rezra.com
On May 2, 2006, at 1:49 PM, Mark Lewis wrote:
They are not equivalent. As I understand it, RAID 0+1 performs
about
the same as RAID 10 when everything is working, but degrades much
less
nicely in the presence of a single failed drive, and is more
likely to
suffer catastrophic data loss if multiple drives fail.
-- Mark
On Tue, 2006-05-02 at 12:40 -0600, Brendan Duddridge wrote:
Everyone here always says that RAID 5 isn't good for Postgres. We
have an Apple Xserve RAID configured with RAID 5. We chose RAID 5
because Apple said their Xserve RAID was "optimized" for RAID 5.
Not
sure if we made the right decision though. They give an option for
formatting as RAID 0+1. Is that the same as RAID 10 that everyone
talks about? Or is it the reverse?
Thanks,
___________________________________________________________________
_
Brendan Duddridge | CTO | 403-277-5591 x24 |
brendan@xxxxxxxxxxxxxx
ClickSpace Interactive Inc.
Suite L100, 239 - 10th Ave. SE
Calgary, AB T2G 0V9
http://www.clickspace.com
On May 2, 2006, at 11:16 AM, Jim C. Nasby wrote:
On Wed, Apr 26, 2006 at 05:14:41PM +0930, Eric Lam wrote:
all dumpfiles total about 17Gb. It has been running for 50ish hrs
and up
to about the fourth file (5-6 ish Gb) and this is on a raid 5
server.
RAID5 generally doesn't bode too well for performance; that
could be
part of the issue.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
---------------------------(end of
broadcast)---------------------------
TIP 4: Have you searched our list archives?
http://archives.postgresql.org
---------------------------(end of
broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your
desire to
choose an index scan if your joining column's datatypes do
not
match
---------------------------(end of
broadcast)---------------------------
TIP 6: explain analyze is your friend
---------------------------(end of
broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
---------------------------(end of
broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
