Re: questions about io scheduler

From: Bill Davidsen
Date: Tue Mar 09 2004 - 15:18:55 EST

Mike Fedyk wrote:
Timothy Miller wrote:

Mike Fedyk wrote:

Nick Piggin wrote:

Kyle Wong wrote:

2. Does io scheduler works with md RAID? Correct me if I'm wrong,
io-schedular <--> md driver <--> harddisks.

It goes md driver -> io schedulers -> hard disks.

There is an IO scheduler per disk.

So MD submits the data to each disk through the IO scheduler.

This allows you to have the heads on each disk in the array at different locations, and helps keep response times lower for seeky loads.

Say you've got a RAID1. In this case, MD could send the read request to either device. How does it decide which one to use?

The one with the drive head closest to the data.

Or hopefully the one not in use if one is busy...

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