[Sussex] Raid install

[Stephen Williams]

On Sat, 2005-09-10 at 11:42 +0100, Dave Chapman wrote:
> On Saturday 10 September 2005 10:57, Stephen Williams wrote:
> > On Sat, 2005-09-10 at 06:00 +0100, Steve Dobson wrote:
> > > Dave
> > >
> > > On Fri, Sep 09, 2005 at 11:18:06PM +0100, Dave Chapman wrote:
> > > > Are there any caveats for installing to a raid0 partition.
> > > > I believe that I will need a /boot and swap on a non raid drive.
> > >
> > > You are correct.  The /boot partition (where your kernel lives)
> > > needs to be on a non-raid partition as the boot loader (grub
> > > lilo) that is installed in you MBR one the boot partition is not
> > > raid aware.
> >
> > Alternatively, if you're only planning to use 2 disks in an array, you
> > can create an identical partition on each disk, set each type as linux
> > (83), use the partition on the first disk in the array as a standard
> > linux /boot partition, and set your BIOS to boot from the RAID device.
> > Any other partitions can be set to linux raid autodetect and used to
> > create the necessary RAID arrays.
> >
> > > I'm not sure about this but I think swap can be on any device.
> > > The problem with running software raid is the the raid device
> > > must be set up before swap is mounted - much easier to make
> > > swap a native disk partition.
> >
> > I run swap on RAID 1 arrays without a problem. If you compile MD support
> > into the kernel, the arrays are created automatically by the kernel and
> > are ready to go by the time swap is initialised.
> >
> > > > I'm not too bothered if the system crashes if a hard drive
> > > > fails thats why I have not mirrored the drives Just as long
> > > > as my /home survives. So thats on /dev/hdb
> >
> > That's fine, but your system is at risk if either of the RAID 0 drives
> > fails. Effectively you have double the chance of a fatal disk error
> > occurring. I'd seriously think about using RAID 1 arrays here. If you
> > follow the setup above, you can copy the contents of /boot on RAID disk
> > 0 to RAID disk 1, and use grub to setup the MBR of RAID disk 1 as well.
> > This means that in the event of a RAID disk 0 failure, you can set your
> > RAID disk 1 to be the boot disk and carry on as before. The advantage of
> > this is that when you get a new replacement disk, you can sync the new
> > disk to the existing one using the RAID controller's built in management
> > system.
> >
> > > Well a hard drive crash may happen to any disk.  If it happens
> > > to your /dev/hdb then you will loss your /home partition anyway.
> > >
> > > If you were to mirror and mount /home on the mirrored partition
> > > then in order to lose /home *ALL* disks in the mirror would
> > > have to fail.
> >
> > Yup, I recommend RAID 1 for /home too.
> There's a chance I can get a compaq cage to take 5x 9.1GB disc's so a raid 5 
> setup for /home would be good yes ?

I'd set up 2 x 9.1Gb disks as a RAID 1 array for /boot, swap and /, with
3 x 9.1Gb disks as an 18.2Gb (approx) array for /home

Steve W.

> This would depend on how much fan noise and disc spin noise it generates as to 
> how acceptable to the wife it is.
> 
> And partion /dev/hda with
> hda1= /windows/XP
> hda2= /boot
> hda3= /windows/fat
> 
> Thanks
> Dave
> 
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