On 04/14/2011 08:04 AM, Christopher Chan wrote:
>
>> Then try both for your use case and your hardware. We have wide raid6 setups
>> that does well over 500 MB/s write (that is: not all raid6 writes suck...).
>>
> /me replaces all of Peter's cache with 64MB modules.
>
> Let's try again.
If you are trying to imply that RAID6 can't go fast when write size is
larger than the cache, you are simply wrong. Even with just a 8 x RAID6,
I've tested a system as sustained sequential (not burst) 156Mbytes/s out
and 387 Mbytes/s in using 7200 rpm 1.5 TB drives. Bonnie++ results
attached. Bonnie++ by default uses twice as much data as your available
RAM to make sure you aren't just seeing cache. IOW: That machine only
had 4GB of RAM and 256 MB of controller cache during the test but wrote
and read 8 GB of data for the tests.
Version 1.96 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -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
xxxx 8G 248 99 155996 74 85600 42 961 99 386900 62
628.3 29
Latency 33323us 224ms 1105ms 19047us 77599us
113ms
Version 1.96 ------Sequential Create------ --------Random
Create--------
xxxx -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
/sec %CP
16 17395 56 +++++ +++ 23951 61 27125 84 +++++ +++
32154 84
Latency 330us 993us 980us 344us 64us
80us
--
Benjamin Franz