I have a rescue system on the same USB stick (it's 1GB).
So I can have a full linux system to debug my RAID if there should be
problems.
For me LVM doesn't really make any difference the limiting factor is
dmcrypt. Still the RAID5 with LVM+crypto+xfs does ~100MB/s sequential
reading. (>300MB/s from md0 directly) That's more than I need.
Kind regards,
----- Message from majedb@xxxxxxxxx ---------
Date: Tue, 8 Sep 2009 15:36:53 +0300
From: "Majed B." <majedb@xxxxxxxxx>
Subject: Re: Software Raid 5 work on ROOT ?
To: Nagilum <nagilum@xxxxxxxxxxx>
Cc: lfmarante@xxxxxxx, linux-raid@xxxxxxxxxxxxxxx
I was able to install & boot Slamd64 (a 64-bit port of Slackware) with
raid5 directly. I wrote a HOWTO on Slamd64's forums, but I can't
access them now, but luckily I wrote a copy of my own:
http://mbhtech.blogspot.com/2008/01/raid-expansion-and-beauty-of-xfs.html
You'll need to put separate /boot from the rest, and I don't know
whether this works with grub or not; I used LILO.
I faced one problem a few months back where the array broke (one disk
jumped out) and I couldn't access my system at all, because the system
wouldn't boot from a degraded array. I had to put the installation CD
and fix it from there.
Maybe if I had compiled busybox into the kernel, I would've saved
myself some trouble. Also, I read a few days back that you could pass
a parameter to the kernel to make it boot a degraded array. I don't
remember where or what the syntax was unfortunately.
I hope this helps!
P.S.: I'd skip LVM. I've been speed-testing it lately and its
performance is quite crippling. The read speed of the array directly
is 125 MB/s, while the Logical Volume reads at 43 MB/s only!
2009/9/8 Nagilum <nagilum@xxxxxxxxxxx>:
The way I worked around this is to boot off of a USB stick.
So grub is installed on the USB stick, reads the kernel and the initrd from
it, the initrd brings up the disk, the raid, the dm-crypt and the lvm,
mounts / from the lvm and boots it.
Kind regards,
----- Message from lfmarante@xxxxxxx ---------
Date: Fri, 04 Sep 2009 12:19:23 +0200
From: lfmarante@xxxxxxx
Subject: Software Raid 5 work on ROOT ?
To: linux-raid@xxxxxxxxxxxxxxx
Hello every body.
I have a question in regard of booting linux under a raid 5. It is
possible ?
All the guides that I found on the net say to have a /boot not stripped,
(raid1
is ok). [EX:
http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml
]
They say to have / not stripped too. And these guide show to have an raid
1 boot
and / and create a LVM volume for /usr /opt /var /whatever that can be
raid 5.
It is not easiest to have directly / in raid 5 format ?
If it's possible I would prefere to have raid 5 /
There any particular configuration for grub to boot it?
Thanks in advance.
----- End message from majedb@xxxxxxxxx -----
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