Re: software raid does not do parallel reads under 2.4?

[Daryll Strauss]

On Fri, Aug 24, 2001 at 07:01:40PM +0200, Wilfried Weissmann wrote:

> I experienced some performance loss when moving from kernel 2.4.4 to
> 2.4.7-ac3 regarding ide harddisks. I am useing the hpt ataraid driver
> which does pretty much the same thing as the md disk striping driver.
> I/O speed of the raid volume is about as fast as accessing a single
> drive.
> There were a lot of ide reports some time ago. Maybe they where problems
> with concurrent I/O operations...?

I'm seeing similar behavior with SCSI. I've got two SCSI channels. If I
run two dd's each talking to disks on different channels, I get 2x disk
bandwidth. If I run two dd's talking to disks on the same channel I get
1x disk bandwidth. This is with 2.4.9, but I haven't isolated which
kernel versions cause this.

This system has 8 U160 disks spread over 2 U160 channels and it hasn't
been deployed yet, so if I can help with testing, let me know.

						- |Daryll