[PLUG] IDE RAID and Linux (revisions)

[Launi]

Your input helps, thanks. I'm going to going to buy one more SIIG IDE 2
channel controller and start putting the hardware together.  I'll then start
the install and try software Raid 5. 

______________________________________________
Lonnie Wormley



  >-----Original Message-----
  >From: plug-admin at lists.pdxlinux.org 
  >[mailto:plug-admin at lists.pdxlinux.org] On Behalf Of Steve Beattie
  >Sent: Saturday, March 15, 2003 7:18 PM
  >To: plug at lists.pdxlinux.org
  >Subject: Re: [PLUG] IDE RAID and Linux (revisions)
  >
  >
  >Hey Launi,
  >
  >I'm going to preface my response by saying that I've only 
  >used software raid (on ide) under linux, not hardware ide 
  >raid (though I've seen others I work with beat their heads 
  >against the wall with hardware raid driver issues).
  >
  >On Sat, Mar 15, 2003 at 02:25:36PM -0800, Launi wrote:
  >> I'm going to build a replacement Linux server for one of my aging 
  >> servers and want to do RAID 5.  I have done hardware SCSI RAID on 
  >> Window$ so I know how it works in principle.  I have never done 
  >> software IDE RAID before.  I have a few questions before I 
  >get started 
  >> that may save me aggravation later on. I understand that the Linux 
  >> 2.4.x kernel supports software RAID and I also know that 
  >in order to 
  >> get the best performance you need your IDE drives on one 
  >channel each.  
  >> I want RAID 5 with one hot spare using 4 identical 72 GB drives.
  >
  >To be pedantic, the 2.2 linux kernels also support software 
  >RAID, which is what I'm using. My understanding is that the 
  >software RAID format is the same between 2.2 and 2.4, but 
  >don't know about 2.5 (I know there's been drastic changes in 
  >the LVM stuff, not sure how it's affected software RAID).
  >
  >> I'm open to using any Linux distribution that will make 
  >this work.  I 
  >> have used RedHat, Mandrake and Debian in the past.
  >
  >AFAIK, they all will make it work. On the other hand, I have 
  >no idea how well the installers handle it -- I set mine up 
  >manually long after install time, as I was adding a mirror 
  >drive for a system without backing up and reinstalling -- I 
  >had no backup device that could store the amount of data reasonably.
  >
  >>  1. Can I just have my 4 IDE drives connected to two separate two 
  >> channel PCI IDE controllers and Linux will recognize them during 
  >> startup?
  >
  >I believe so, my raid 1 setup is two drives, one on each 
  >channel of the ide controller. 
  >
  >> 2. If I do buy a 4 channel controller (Rocket Raid 404) 
  >which does not 
  >> support RAID 5 via hardware, will Linux support it using software?
  >
  >Likely so (modulo my inexperience with hardware raid). 
  >Essentially you'd be using it as a straight 4 channel ide 
  >controller, no raid as far as the hardware device is concerned. 
  >
  >> 3. Should I only use the controllers listed here 
  >> (http://www.tldp.org/HOWTO/Hardware-HOWTO/ideraid.html)?
  >
  >Dunno. You probably should also look at what the 
  >distribution you plan on using supports for hardware raid, 
  >if that's the way you decide to go.
  >
  >>  4. If I'm not concerned about performance can I use one 2 
  >channel PCI 
  >> IDE controller and connect the four drives (two on each channel)?
  >
  >In software raid, I'm almost certain it will. All it looks 
  >at are the block devices you give it, I don't think it has 
  >any meta knowledge about them. You likely could be able to 
  >mirror across a mix of scsi, ide, cf or other random 
  >devices, assuming they present themselves as block devices 
  >(not having tried it, I don't this for sure, but it seems like it). 
  >
  >> Basic RAID configuration questions
  >>  
  >>  1. If I use Linux software RAID without a hardware driver 
  >should I 
  >> boot off a single disk and then make RAID for just my data?
  >
  >You can, but you don't have to, you can have the root 
  >partition on raid as well (I do this).  You will have to use 
  >an initrd (ram disk) with the software raid modules (md) in 
  >it or have a kernel with software raid compiled in so that 
  >the kernel has access to the software raid driver before any 
  >of the file systems have been mounted.
  >
  >> 2. If I have hardware
  >> RAID with Linux driver support can I install directly on the RAID?
  >
  >Yes, I believe so.
  >
  >> I'm on a budget and this is a home business system so that 
  >I can store 
  >> my clients graphic work.  If I can use one PCI card with 4 ATA 
  >> controllers on it at a cost of $100 then this would be 
  >ideal.  If I 
  >> have to go with a higher end SX6000 or Escalade 7500-4 ATA 
  >133 RAID 
  >> Controller Card then I would have to spend about $300.  
  >I'll spend the 
  >> money if that's what it takes to work, but I wanted to use Linux 
  >> software RAID and did not want to have to deal with third party 
  >> hardware drivers.
  >
  >I've been very happy with linux's software raid, though I've 
  >not had a disk failure -- I did have to run in a failed 
  >configuration for a while while I was moving my data from 
  >non-raid to raid. Personally, I'd lean towards a raid 0+1 
  >(or is it 1+0 that's the better of the two? I never
  >remember) if I had four disks and was willing to give up 
  >some space, but that's just me.
  >
  >Hope this helps.
  >
  >-- 
  >Steve Beattie                               Don't trust programmers?
  ><steve at wirex.net>                         Complete 
  >StackGuard distro at
  >http://NxNW.org/~steve/                            immunix.org
  >http://www.personaltelco.net -- overthrowing QWest, one 
  >block at a time.
  >