[rhn-users] software raid

[Jon Branch]

Hi Matt 
 
If you want to use sofware RAID on Linux I recommend you get "Managing RAID on Linux" by Derek Vadala, published 
by O'Reilly. 
 
The easiest way to set up RAID on Linux initially is by doing a clean install. The set up of the RAID devices is 
pretty much a point and click operation using the Disk Druid partitioning tool. How to do this is covered in the 
Red Hat installation guide. 
 
Please note that RAID 0 does not provide any redundancy; RAID 1 (mirroring) does. Also please note that your /boot 
and / partitions need to be RAID 1. 
 
I use Linux RAID on two servers I manage and it works really well. I use the mdadm tool for management rather than 
raidtools as I find it better. A word of caution though. Don't totally rely on any RAID array to provide foolproof 
protection of your data. I have had the experience, using a hardware RAID controller on a Windows 2000 box, of 
having the RAID controller fail and corrupt both hard disks in the mirror (in fact both disks failed at the same 
time). So always have another backup somwhere! 
 
Regards 
 
Jon Branch 
IT Coordinator - Christian Alliance International School - Hong Kong 
----- Original Message ----- 
From: Matt Allen <mallen at theebizshop.net> 
Date: Mon, 19 Jul 2004 15:20:59 -0500 
To: Red Hat Network Users List <rhn-users at redhat.com> 
Subject: Re: [rhn-users] software raid 
 
> On Monday 19 July 2004 11:03, Kvetch wrote: 
> > I have a machine with 2 identical IDE drives in them.  I know I can 
> > setup a software raid 0 partition which will enable a RAID mirror for 
> > that partition.  Is there a way I can setup software RAID 0 to work 
> > like a hardware RAID so it clones everything on the drive?  So can I 
> > just create one RAID device across the 2 drives and every partition I 
> > create under the RAID devices is duplicated on second drive, including 
> > the boot and / partition?  This way if either drive die I can work off 
> > one drive until the second drive is replaced? 
>  
> First off, RAID 0 is striping, RAID 1 is mirroring. If you set up RAID 0 and  
> lose one of your drives, all of your data is toast. 
>  
> I don't know what release you're running, but under RHELv3 you use the RedHat  
> partitioning tool (Disk Druid) to set up identical partitions on each drive.  
> So, if you've got two drives and you want three partitions plus your swap,  
> then create those three partitions on both drives, selecting the "Software  
> RAID" option for partition type. (Note: You must create a swap partition on  
> each drive, and they will not be involved in the RAID setup). 
>  
> It should look something like this: 
>  
> First drive: 
> /dev/hda1		software raid		10GB 
> /dev/hda2        software raid		8GB 
> /dev/hda3		software raid		5GB 
> swap 
>  
> Second drive: 
> /dev/hdb1		software raid		10GB 
> /dev/hdb2		software raid		8GB 
> /dev/hdb3		software raid		5GB 
> swap 
>  
> Once all of your Software RAID partitions are in place on both drives, select  
> the RAID option and then create a RAID 1 device. Pick your mount point, FS  
> type, and select two of the identical partitions (e.g, hda1 and hdb2). Repeat  
> this step until all of your RAID devices are configured.  
>  
> You'll get something like this: 
>  
> /dev/md0		ext3			10GB (mount point is listed somewhere) 
> /dev/md1		ext3			8GB 
> /dev/md2		ext3			5GB 
>  
> I don't have Disk Druid in front of me so I can't check if all my terms are  
> correct, and the layout of the information in Disk Druid is not identical to  
> my notes above, but that is the gist of software RAID set up. 
>  
> I haven't had a drive fail in any of my software RAID sets yet, so I don't  
> know what recovery is like, but ideally you'd just run off of the good drive  
> until you replace the bad, like you said. 
>  
> Cheers, 
> Matt 
>  
>  
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