[CentOS] software raid

[Feizhou]

Joshua Baker-LePain wrote:
> On Thu, 29 Mar 2007 at 12:17pm, chrism at imntv.com wrote
> 
>> I keep hearing about this "slowness" thing.  Here is a bonnie++ run on 
>> one of my spare machines.  This particular machine is also running 4 
>> copies of Folding at Home in the background during the test.  The array 
>> being tested is on a 3Ware 9550 card with 8 500gig barracudas.  The 
>> filesystem is a standard ext3 filesystem with zero tweaks.  It doesn't 
>> appear that slow to me, but perhaps I'm just easy to please.
> 
> The problem was particularly pronounced on the 75xx/85xx series cards 
> (which were not exactly RAID5 speed demons).  XFS blew away ext3 on 
> hardware RAID5 arrays on those cards.  I don't have any benchmarks handy 
> on 95xx series cards, bit I vaguely recall that XFS still performed 
> better, but not by anywhere near the same margin.
> 

The 75xx and 85xx boards suffered from lack of onboard memory which 
meant that they had to wait for the disks to be done before returning 
A-OKAY. I am talking about RAID5 arrays as raid1, raid0 and raid10 
arrays on these boards were okay. XFS should still wipe the floor with 
ext3 on the 95xx series on raid5 arrays due to problems with the code in 
the kernel between ext3 and the 3ware driver.