Re: Raid 5 on Fedora 4 working with SATA ?

Gilboa Davara wrote: 
On Wed, 2006-02-01 at 09:45 +0000, Terry Barnaby wrote:

Hi,

I have just set up a Raid 5 disk array using 4 SATA disks on Fedora 4.
To test the setup I unplugged the SATA cable from one of the disk drives.
I was expected the system to carry on with messages from the Raid system
indicating that there was a disk drive down.

However the Raid 5 partition became completely inaccessable after un-plugging
the drive. The kernel reported disk errors but there was no error messages
from the Raid system and "mdadm -Q --detail /dev/md2" reported that there
was no problems with the Raid array.

When I rebooted the system (needed a reset) the Raid system reported that
one disk was down and the partition became readable again.

It appears that the default configuration of the Raid 5 system does not
handle a complete drive failier during up-time. I presume it may respond to
disk errors from a disk drive that is connected but once disconnected the
Raid system appears to ignore errors.

Is there a configuration option to allow the Raid system to respond to
a completely broken drive or cable ?

Terry



A. Are you sure your machine/controller hot plug? SATA doesn't support
it by default. (You'll need special drive enclosures and
hot-plug-supporting controller.
B. Can you post your complete machine configuration?

Gilboa

Hi,

Thank you for the response.

A. No, I don't think the SATA controller is a hot-plug-supporting controller.
It is a: "Intel Corporation 82801FB/FW (ICH6/ICH6W) SATA Controller (rev 04)".

B.
Motherboard:	AOPEN i915Ga-PLF
CPU:		Pentum 4 3GHz
Disks:		4 * SATA WD Caviar 320G

Paritions:	Each disk has: 1 - 20G, 2 - 1G (swap), 3 - ~300G
Raid:		"/"      /dev/md0 Raid1 using /dev/sda1,/dev/sdb1
		"/spare" /dev/md1 Raid1 using /dev/sdc1,/dev/sdd1
		"/data"  /dev/md2 Raid5 using /dev/sda3,/dev/sdb3,/dev/sdc3,/dev/sdd3

Although the SATA controller is not a "hot-plug" controller I assumed that
disconnecting a SATA disk to simulate a cable failier or complete drive failier
would cause the RAID system to react correctly. Certainly I see kernel
error messages from the disk/controller in question and I would have assumed that
the RAID system would react to this ...

Terry
	

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