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.