Re: Benchmarks: Linux Kernel RAID vs a Hardware RAID setup

[Bill Davidsen <davidsen@tmr.com>]

Keld Jørn Simonsen wrote:
> On Wed, Jul 16, 2008 at 01:58:05PM +1000, Ben Martin wrote:
>   
>> On Tue, 2008-07-15 at 18:39 +0200, Keld Jørn Simonsen wrote:
>>     
>>> On Wed, Jul 16, 2008 at 12:06:09AM +1000, Ben Martin wrote:
>>>       
>> One interesting question about the r10 layouts, if f2/o2 perform better
>> than n2 why is the default for creation still n2? Just like mkfs.xfs
>> determining the raid chunk and stripe size for you (assuming you don't
>> use LVM to circumvent this, gah!), shouldn't mdadm select the "fastest"
>> --layout as the default for RAID-10?
>>     
>
> Perhaps. I think Neil first implemented "near", and more or less at the same
> time "far" - but to him the main thing was "near". This was 2.6.9. Then
> in 2.6.18 he implemented "offset".  In the early days the
> characteristics of each layout were not well known. It is only in the
> last year or so I have seen benchmarks with n2, f2 and o2.


I admit that I have done "raw device performance" benchmarks with n2 and 
f2, and neglected o2 completely, so I rely on other's work. However, I 
am most often bitten by raid5 issues, so I have been paying most 
attention to them.

-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 



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