On Thursday, April 14, 2011 11:26 PM, Benjamin Franz wrote:
> 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.
Wanna try that again with 64MB of cache only and tell us whether there
is a difference in performance?
There is a reason why 3ware 85xx cards were complete rubbish when used
for raid5 and which led to the 95xx/96xx series.
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