13 aug 2008 kl. 17.13 skrev Decibel!:
On Aug 11, 2008, at 9:01 AM, Jeff wrote:
On Aug 11, 2008, at 5:17 AM, Henrik wrote:
OK, changed the SAS RAID 10 to RAID 5 and now my random writes are
handing 112 MB/ sek. So it is almsot twice as fast as the RAID10
with the same disks. Any ideas why?
Is the iozone tests faulty?
does IOzone disable the os caches?
If not you need to use a size of 2xRAM for true results.
regardless - the test only took 10 seconds of wall time - which
isn't very long at all. You'd probably want to run it longer anyway.
Additionally, you need to be careful of what size writes you're
using. If you're doing random writes that perfectly align with the
raid stripe size, you'll see virtually no RAID5 overhead, and you'll
get the performance of N-1 drives, as opposed to RAID10 giving you N/
2.
But it still needs to do 2 reads and 2 writes for every write, correct?
I did some bonnie++ tests just to give some new more reasonable numbers.
This is with RAID10 on 4 SAS 15k drives with write-back cache.
Version 1.03b ------Sequential Output------ --Sequential Input-
--Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec
%CP /sec %CP
safecube04 32136M 73245 95 213092 16 89456 11 64923 81 219341
16 839.9 1
------Sequential Create------ --------Random
Create--------
-Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP /sec %CP
16 6178 99 +++++ +++ +++++ +++ 6452 100 +++++ +++
20633 99
safecube04,32136M,
73245,95,213092,16,89456,11,64923,81,219341,16,839.9,1,16,6178,99,++++
+,+++,+++++,+++,6452,100,+++++,+++,20633,99
--
Decibel!, aka Jim C. Nasby, Database Architect decibel@xxxxxxxxxxx
Give your computer some brain candy! www.distributed.net Team #1828
