Danilo,

If I have a h/w support for IDE hot swap then what do you recommand for
the same as you suggested for scsi below?

Thansk,

Bo
----- Original Message -----
From: "Danilo Godec" <redacted>
To: "Maurice Hilarius" <redacted>
Cc: "Linux-raid" <redacted>
Sent: Thursday, April 18, 2002 11:20 PM
Subject: Re: couple of seemingly dumb questions

On Thu, 18 Apr 2002, Maurice Hilarius wrote:

quoted

On software RAID/raidtools how does one change the rebuild priority on a
replacement disk or resync?
I don't mind giving higher CPU priority, since in many cases the boxes I

am

quoted

using have lots more CPU than is being used most of the time.

With 2.2 kernels, you can simply use 'cat /proc/sys/dev/md/speed-limit',
to see the *minimum* rebuild rate. You can change it using
'echo 200000 > /proc/sys/dev/md/speed-limit'.

With 2.4 kernels, there are two files in '/proc/sys/dev/raid/', called
'speed_limit_max' and 'speed_limit_min'. I think the rest is pretty
obvious.

quoted

Secondly:
With a software RAID5 setup, with disks in removable hot-swap trays, I

want

quoted

to be able to pull a failed disk and replace it and have it then

rebuild.

quoted

Problem is, when I pull the disk I get lots of error messages, and then
when I replace it there is nothing happening to redetect that the disk

is

quoted

changed, and allow me to rebuild. If I reboot then the machine does

resync

quoted

with the new drive, but surely there must be a way without a reboot?

I suppose you have SCSI disks (I think hot-swap IDE is just not that far
along).

First you have to make sure, that the failed disk is not in use anymore.
This means using 'raidhotremove' for every partition of that disk, that
may be in use (also check for non-RAID partition, if they exist). When
you're sure the disk is not used anymore, make the kernel 'release' the
disk from SCSI bus using:

echo "scsi remove-single-device 0 1 2 3" >/proc/scsi/scsi

Check 'cat /proc/scsi/scsi' to check if the failed disk is still listed.
If it is, it's probably still in use and can't yet be removed. Re-check
the first step... Else, you can pull the disk out and install a new one.

Before you can use the new disk, you have to make the kernel accept it to
SCSI. Use:

echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi

Check 'cat /proc/scsi/scsi' if the new disk has appeared. If it has,
you're all set to partition the disk and use it at will.

   D.

PS: See /usr/src/linux/drivers/scsi/scsi.c for more about this
/proc/scsi/scsi commands.

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