root on raid: re-arranging disks?

Subject: root on raid: re-arranging disks?
From: Mac Mason (macmasta@ak.net)
Date: Wed Dec 05 2001 - 20:53:12 AKST

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I was benchmarking hard drives today, and found something interesting.
I have hda and hde on a RAID-0.
Hde is on a pci-based ata100 controller.
now, with hdparm twiddled a little (-c 1 -d 1) I get the following:

hdparm -t /dev/hda gives me 38.55 MB/sec
hdparm -t /dev/hde gives me 9.04 MB/sec
hdparm -t /dev/md0 (the raihdparm -t /dev/hdad device) gives me 18.71
MB/sec

Anyone else see my offboard drive cutting into my performance?
So the question is twofold:
First, I know that doing a mkraid hoses data. I don't want to hose my
data, but I'd like to bring the 2nd HDD onto the motherboard controller,
and see if that helps. Guess what, though: / is on /dev/md0. editing
/etc/raidtab is easy, but how do I change the autodetection superblocks
to the new drive letters without hosing it?

Anyone have a link to a good set of pointers for hdparm, btw? I improved
performace markedly by twiddling just a bit: I wonder if more could get
me more.

Thanks!

~Mac~

• Next message: Mac Mason: "Found a solution, and a note for the guy who was curious about putting two devices on one IDE channel"
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