Re: [SLE] hotswap sata disks

On Mon, 2006-07-31 at 18:51 -0400, Greg Freemyer wrote:
On 7/31/06, Roger Oberholtzer <roger@xxxxxx> wrote:
Of course hot swapping SATA disks is not currently supported in Linux.
As such, udevmonitor reports nothing when the disks are inserted or
removed on a system that does support this at the hardware level. There
is work in libata, but nothing functioning for use in a production
system.

Not sure how "production" you need it to be.

Mere mortals will need to use it. So it can't require fiddling. And it
should be reliable. I wonder which SATA controllers are supported. I
have an Intel 82801GB/GR/GH (ICH7 Family).

The 2.6.17 kernel has been out for a couple months I think.

Interesting. I'm using 2.6.16.13-4-smp on SUSE 10.1. Close but no
cigar.

Seems there is no kernel-of-the-day for 2.6.17. Unless it is somewhere
other than in http://ftp.suse.com/pub/projects/kernel/kotd/ or I am
looking in the wrong directory.

I don't relish installing a new vanilla kernel as it messes up all the
SUSE kernel packaging. Any other options?

Maybe I can just update the libata.ko module. Probably not, as that
would potentially be too easy.

There is a stable libata patch to add hotswap capability to it. It
still has a nasty experimental warning I think in the readme, but in
the several months it has been out, there really have been very few
issues and none I recall caused data loss. I would definately
consider it.

I wonder if this patch could be applied to the 2.6.16 kernel used in
SUSE 10.0. I have looked at the libata patch directory and it seems it
is a complete patch against the kernel. And that directory is not clear
what is the start point to patch. Maybe I should just download a 2.6.17
kernel, grab libata, and see what happens.

The patch is also in 2.6.18-rc3, but that I too would stay away from.
Not because I don't trust the patch, it is the rest of 2.6.18-rc3 I
would worry about.

Quoting the July 10 announcement e-mail:
=====
Updated version available.

* Link resume handling in the previous version was broken causing libata
to ignore hotplug event after a link has been hot-unplugged. Fixed.

* A few other hotplug related problems are fixed.

I expect this version to have well-behaving PMP and hotplug support. If
anything seems weird, please report.

More info can be found at the following URL.

http://home-tj.org/wiki/index.php/Libata-tj-stable

Updated patches against v2.6.17.4 are at the following URL.

http://home-tj.org/files/libata-tj-stable/libata-tj-2.6.17.4-20060710.tar.bz2


So, what would be the next best thing? I assume I would need to do a
script that handles un-mounting the disks, and then a rescan of the
devices. And then a re-mount.. I remember doing this way back with SCSI
devices. But perhaps there is a best way to scan for SATA devices?

The tricky bit is that I have 4 SATA disks that will sort of work in
sets. And the user will probably want to pop in one in the set when
looking for something.

I do seem to be rambling a bit, but it is because I can't decide the
best approach.

--
Roger Oberholtzer

OPQ Systems AB
Ramböll Sverige AB
Kapellgränd 7
P.O. Box 4205
SE-102 65 Stockholm, Sweden

Tel: Int +46 8-615 60 20
Fax: Int +46 8-31 42 23


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--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century

--
Roger Oberholtzer

OPQ Systems AB
Ramböll Sverige AB
Kapellgränd 7
P.O. Box 4205
SE-102 65 Stockholm, Sweden

Tel: Int +46 8-615 60 20
Fax: Int +46 8-31 42 23


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