But this is doing disk "reads" not "writes". It shouldn't need to read from
both disks.
From
http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/Software-RAID.HOWTO-2.html#ss
2.3
For RAID1:
Read performance will usually scale close to to N*P, while write performance
is the same as on one device, or perhaps even less. Reads can be done in
parallel, but when writing, the CPU must transfer N times as much data to
the disks as it usually would (remember, N identical copies of all data must
be sent to the disks).
I should expect at least the same performance (when disks are on the same
bus) -- that's why I'm confused. I would actually expect better performance
given that the limit is the disk i/o speed and not the data bus. If disks
were on seperate buses I would expect better performance.
________________________________________
Michael D. Black Principal Engineer
[EMAIL PROTECTED] 407-676-2923,x203
http://www.csi.cc Computer Science Innovations
http://www.csi.cc/~mike My home page
FAX 407-676-2355
----- Original Message -----
From: Andy Poling <[EMAIL PROTECTED]>
To: Mike Black <[EMAIL PROTECTED]>
Cc: raid <[EMAIL PROTECTED]>
Sent: Monday, August 30, 1999 9:10 AM
Subject: Re: Why RAID1 half-speed?
On Mon, 30 Aug 1999, Mike Black wrote:
> I just set up a mirror this weekend on an IDE RAID1 - two 5G disks on the
> same IDE bus (primary and master).
>
> I was under the impression that I shouldn't see any slowdown and maybe
even
> a speedup but, alas, it is not so.
If you're at all concerned about speed, you should not be putting both disks
on the same IDE controller.
-Andy
