[CentOS] Re: Read performance on software RAID1?

Thu Apr 12 18:47:58 UTC 2007
WipeOut <wipe_out at users.sourceforge.net>

Scott Silva wrote:
> WipeOut spake the following on 4/12/2007 9:38 AM:
>> Hi,
>>
>> Since the data is available in two places on a RAID1 array does the code
>> in any way make use of that for improved performance by reading
>> (different) data form both disks at the same time? Or is the one disk
>> simply a slave that just receives copies of the data and is never really
>> read from at all?
>>
>> Thanks
> AFAIR asks for the data from the raid device, and the md code sends the
> request to both drives. The drive that replies with data first is the winner.
> So the system would be reading staggered by that method. Now writes are a
> different story.

Ok, so in theory then read performance on software RAID1 may be better 
than a single disk but how much better would depend on the hit rate of 
the requests being distributed..

Whats the story on writes?
You make it sounds like there is something happening there that you are 
not happy about..