Date: Thu, 16 Sep 1999 07:48:33 +1000 (EST) From: Andrew MacIntyre <andymac@bullseye.apana.org.au> To: Andriss <andriss@andriss.com> Cc: questions@FreeBSD.ORG Subject: SCSI drive mirroring (was Vinum Concerns) Message-ID: <Pine.OS2.3.95.990916073442.842A-100000@CENTRAL> In-Reply-To: <Pine.BSF.4.10.9909150107420.71944-100000@netmint.com>
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On Wed, 15 Sep 1999, Andriss wrote:
> Yes the drives are absolutely identical (u2w SCSI: IBM UltraStar 18es)
{...}
> Can you tell me what parameters I should use with dd? Reading the
> manual page is think this should be used:
>
> dd if=/dev/rda0 of=/dev/rda1
>
> Important assumption: da0 is source, and da1 is destination.
That's what I'd be using, at least initially. Its possible that you could
use a larger block size (bs=) to improve performance, but verify it works
first!
> ...And what do you mean watch out for effects of open files?
> Could you explain that one please?
Given the way you phrased the original question, I was assuming that the
source drive would be your boot drive, and probably be home to various
active log files. I was cautioning to be aware, just as you should be
with all methods of backup used with raw devices which have filesystems
mounted from them, that the state you are backing up may not be 100%
consistent. Particularly in this case, where you may find that the
mirrored drive contains partitions that get fsck'ed when you try and use
them. There are ways to reduce the likelihood of significant problems,
such as shutting down non-essential services for the duration of the
backup, and using "sync" before copying.
This is where a lower level mirroring solution like vinum makes life
easier.
> (and is there a way to list all open files?)
lsof (in ports IIRC).
--
Andrew I MacIntyre "These thoughts are mine alone..."
E-mail: andrew.macintyre@aba.gov.au (work) | Snail: PO Box 370
andymac@bullseye.apana.org.au (play) | Belconnen ACT 2616
Fido: Andrew MacIntyre, 3:620/243.18 | Australia
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