Re: device names for IDE with SATA?
From: Rick Moen (rick_at_linuxmafia.com)
Date: 03/15/04
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Date: Mon, 15 Mar 2004 19:02:00 -0000
Murray Eisenberg <murray@math.umass.edu> wrote:
> This is yet another try to elicit a definitive response to my questions
> below.
>
> System: Intel 875P chipset (on an Abit IC7-MAX3 motherboard) that has
> Intel's built-in SATA support; a pair of SATA drives on that MB SATA
> controller; an IDE drive as primary on 1st IDE channel.
>
> How will these devices be known to Linux?
It depends. Specifically:
> (1) Will the SATA drives definitely be sda and sdb (with no actual
> SCSI devices part of the system), and then the IDE device as hda? Or
> would the SATA drives be hda, hdb, and then the IDE drive as hdc? Or
> would the IDE drive be hda and the SATA drives hdb and hdc?
Just to echo and further explain what André Janz said, there are muliple
Linux drivers capable of supporting your Abit IC7-MAX3 motherboard's
ICH5 SATA chip on the South Bridge. If you use the conventional,
least-effort driver, i.e., the regular drivers/ide ATA driver (using the
Intel PIIX support), then drives attached to the ICH5 will appear as hdX
devices. On the other hand, there's Jeff Garzik's libata driver set,
originated in kernel 2.6 and available as a backport to 2.4.x kernels.
libata's drivers (including the ata-piix driver) generally gives more
stable operation and higher throughput, by using the kernel's SCSI
subsystem. Using libata, your ICH5-attached drives will show up in
Linux as sdX devices.
Clearer? It depends on which of the two driver approaches you use. The
conventional drivers/ide ATA driver set is more easily and automatically
available, but may be subject to freeze-ups (or not, if you're lucky)
and will be relatively limited in its performance limits (which you
might not notice). You could improve in both of those areas by using
libata support, but at the cost of needing to either use a 2.6 kernel
(still a bit exotic) or building a 2.4.x kernel patched to include
libata.
> (2) If the SATA drives are made into a RAID 0 or 1 array, then does
> this change the answers to (a)?
No. RAID or not RAID is irrelevant to that question. Please note,
however, that any RAID array you created on those drives using Intel's
utilities and MS-Windows would be Intel-proprietary software RAID, which
Linux would not be able to understand. That is, Linux would not see
valid filesystems on the block devices (hdX or sdX). Your question #1,
in Linux lingo, would be stated as "What class of block devices would
Linux see my SATA drives as, when connected to my ICH5 chip?" That's a
different question from your #2, which would be stated as "Given a Linux
kernel able to see block devices on my ICH5-connected SATA drives, would
Linux be able to see the RAID volumes' filesystems I created in
MS-Windows?" The answer is no.
> Note that my configuration is to have grub on the MBR of the 1st SATA
> pair (and on the MBR of the SATA array if I set them up as a RAID pair).
GRUB on RAID1 pairs is reported to be a bit problematic. I'd stick to
lilo.
> But Linux itself will be installed on the separate IDE drive, and not on
> the SATA pair. (This is because I'm dual-booting with Windows XP as my
> primary OS.)
So, problem: You've probably set yourself up to already be dependent on
the Intel-proprietary software RAID support in MS-Windows. If you wish
to dual-boot, you're going to have to lose that proprietary RAID.
Sorry.
If you want Linux support for Intel's proprietary software RAID, advise
Intel to start cooperating with the open-source community by giving us
full technical specs and sample driver code without requiring an NDA.
However, the odds are that Intel's software RAID is pretty bad, as such
things generally are. Pity that XP doesn't know how to support _Linux's_
software RAID, which is really quite good.
If Microsoft Corp. would like to know how, we're willing to supply full
technical specs and sample driver code for them to study, without
requiring an NDA. ;->
-- Cheers, * Contributing Editor, Linux Gazette * Rick Moen -*- See the Linux Gazette in its new home: -*- rick@linuxmafia.com <http://linuxgazette.net/>
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