I have some old rack boxes which are going to get some bigger harddrives (IDE/ATA, not SATA) in Spring and I'm wondering if I should put two disks in them and use them as RAID 1 (software RAID). Objective being that the machine can hopefully carry on after (one) disk failure (including rebooting). I don't have any experience with software RAID. Can I do this during the normal CentOS (4) setup or can I even do this later (when there's only one disk and I add another one)? Does it make a difference performance-wise? (slight drop?) Is it reliable, so that it will fulfill on the purpose or should I better forget it? (Replacing the mainboards or adding RAID controller cards is out of the question.) I'm certainly willing to read a How-To or other documentation, but since it's completely new to me I'm not really sure where to start searching.
Kai
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On Sun, Dec 18, 2005 at 08:31:23PM +0100, Kai Schaetzl wrote:
I don't have any experience with software RAID. Can I do this during the normal CentOS (4) setup or can I even do this later (when there's only one disk and I add another one)?
Yes and yes.
Does it make a difference performance-wise? (slight drop?)
In theory, yes, but I never noticed any.
Is it reliable, so that it will fulfill on the purpose or should I better forget it?
Yes, it is reliable.
I'm certainly willing to read a How-To or other documentation, but since it's completely new to me I'm not really sure where to start searching.
Then you should do it at install time. It is fairly straightforward.
Doing it after 1 HD is already started is possible and, once you learn to do it, easy. But it will take you some time to catch all the tricks, so install time is my recomendation.
[]s
- -- Rodrigo Barbosa rodrigob@suespammers.org "Quid quid Latine dictum sit, altum viditur" "Be excellent to each other ..." - Bill & Ted (Wyld Stallyns)
Thanks for all the answers. Can you tell me if this Howto is a good starting point for reading? http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html (It seems a bit old and to only know about lilo. At first glance it doesn't convince me.) Or do you think the info in http://www.centos.org/docs/4/html/rhel-sag-en-4/ is enough to get going?
Kai
--- Kai Schaetzl maillists@conactive.com wrote:
Thanks for all the answers. Can you tell me if this Howto is a good starting point for reading? http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html (It seems a bit old and to only know about lilo. At first glance it doesn't convince me.) Or do you think the info in http://www.centos.org/docs/4/html/rhel-sag-en-4/ is enough to get going?
Kai
-- Kai Schätzl, Berlin, Germany
Hello Kai, I have found this article from Dell to be pretty straightforward. http://www.dell.com/downloads/global/power/1q04-hul.pdf It was written for RHEL3, but all info seems to apply to RHEL4 and it's various rebuilds.
Brett
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Brett Moss wrote on Sun, 18 Dec 2005 15:18:10 -0800 (PST):
I have found this article from Dell to be pretty straightforward. http://www.dell.com/downloads/global/power/1q04-hul.pdf
Thanks, yes, it talks exactly over the stuff that exceeds the basic "how to configure RAID", thanks!
Kai
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On Sun, Dec 18, 2005 at 11:36:03PM +0100, Kai Schaetzl wrote:
Thanks for all the answers. Can you tell me if this Howto is a good starting point for reading? http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html (It seems a bit old and to only know about lilo. At first glance it doesn't convince me.)
That is important reading. Specially for you to understand how things work.
The way to setup the raid itself, tho, is a little different these days.
Or do you think the info in http://www.centos.org/docs/4/html/rhel-sag-en-4/ is enough to get going?
If you are implementing RAID on install time, just go and do it. It is really that simple.
And yes, chapter 10 on that guide will show you how to do it in detail.
[]s
- -- Rodrigo Barbosa rodrigob@suespammers.org "Quid quid Latine dictum sit, altum viditur" "Be excellent to each other ..." - Bill & Ted (Wyld Stallyns)
Rodrigo Barbosa wrote on Sun, 18 Dec 2005 21:52:12 -0200:
That is important reading. Specially for you to understand how things work.
The way to setup the raid itself, tho, is a little different these days.
That is what I assumed, yes, but didn't know for sure. Thanks, I'll it under this premise.
If you are implementing RAID on install time, just go and do it. It is really that simple.
And yes, chapter 10 on that guide will show you how to do it in detail.
Already read, yeah, looks pretty straight-forward, thanks!
Kai
Kai Schaetzl wrote:
Thanks for all the answers. Can you tell me if this Howto is a good starting point for reading? http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html (It seems a bit old and to only know about lilo. At first glance it doesn't convince me.) Or do you think the info in http://www.centos.org/docs/4/html/rhel-sag-en-4/ is enough to get going?
Kai
If you are doing root raid, please also search for "grub mirror" on Google. RHEL4, and therefore Centos 4, does not handle root raid grub installation properly. It will only install on one disk and if that disk goes, you have a non-bootable system. Fedora Core 4 handles this properly from what I hear and so RHEL5 will too when it comes.
Feizhou feizhou@graffiti.net wrote:
Fedora Core 4 handles this properly from what I hear and so RHEL5 will too when it comes.
If you want a good look at what RHEL 5 will be, for starters, check out ... http://fedora.redhat.com/docs/release-notes/fc5/test1-latest-en/
Feizhou wrote on Tue, 20 Dec 2005 00:37:34 +0800:
If you are doing root raid, please also search for "grub mirror" on Google. RHEL4, and therefore Centos 4, does not handle root raid grub installation properly.
Yeah, this has been a point of discussion here recently, but thanks for reminding.
Kai
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Bryan J. Smith -
Feizhou -
Kai Schaetzl -
Rodrigo Barbosa