Re: RAID & /boot

From: Steve Kirkendall (skirkendall_at_dsl-only.net)
Date: 01/14/04 

Date: Wed, 14 Jan 2004 11:05:32 -0800

SR wrote:
> Hello everybody,
>
> a customer has just asked me to get him a server for storage and backup.
> The box will be equipped with 3x250 Gb IDE hard disks, that I'd like to
> configure with software RAID 5 under SuSE 8.2 Pro. I understand it is not
> possible to include the /boot partition in the RAID array, and neither it
> is possible to store it on a floppy because the size of the kernel exceeds
> 1.44 MB.

I have a few of comments to make...

First, although GRUB can't boot from a RAID partition, LILO can. If you
try to install SuSE onto a RAID partition, it will automatically use LILO
as your bootloader, and give you a scary-sounding warning. It seems to
work fine other than that, as far as I can tell.

Second, Linux does RAID on partitions, not whole disks. If you don't feel
comfortable booting from a RAID partition, then simply create a separate
partition for booting. For example, you could build a 6GB partition that
contains all the standard Linux files, and use 244GB for a RAID array that
you mount on /home to store user data. Set up each drive that way. You
could put a copy of the 6GB partition on each drive so that if one fails,
you can bring the system up again by moving cables. (Or even by selecting
"Other Linux" from the boot menu. When I used SuSE to set up disks this
way, it added an entry to the default boot menu for booting from the
non-RAID partition on the second drive -- before I even put a bootable
copy of Linux there.)

For a variety of reasons, it's a good idea to put each hard disk on a
separate controller. Most motherboards only have two IDE controllers,
so you should probably plan to plug in an extra IDE controller card.
Sometimes Linux tries to shuffle the /dev names for the drives when
you do that; if that's a problem, there's a kernel parameter you can
use to prevent it. "ide=reverse", if I recall correctly.

Alternatively, you might consider using disk mirroring with the third
disk as a spare. You would loose storage capacity, obviously, but you'd
gain a little performance and might be able to avoid adding a an extra
IDE controller card. The two active disks should be master disks on
separate controllers, and the spare can be a slave. HOWEVER if the master
drive's electronics or cable fails, then the spare will be inaccessible,
so this isn't the ideal solution. The CDROM drive could be a slave on
the other controller, but it's hard to find a UDMA-133 CDROM drive so
this could reduce the performance of the /dev/hdc hard disk.

I haven't found an arrangement that I'm 100% satisfied with.

Relevant Pages

  • Re: How to Expand HDD on SBS 2003 SP2
    ... Upgrading the disks to larger disks. ... I used various Imaging software to grab images onto an external HDD but had no end of issues with the software either not seeing the drives at all or supposedly successfully re-imaging - and at the same time re-sizing the partitions - only to be non bootable. ... This also gave me the opportunity to create a better partition structure that I could move the data files to later as well. ...
    (microsoft.public.windows.server.sbs)
  • convert dynamic to basic in sbs 2003 (partition size problems)
    ... software mirrored scsii drives split into 3 drives. ... I set the disks up as basic then converted to dynamic (as the original ... My only other options are retest surface, browse partition ... Now Im guessing as these are software mirrors the other way I may be able to ...
    (microsoft.public.windows.server.sbs)
  • Re: What to do about the 2TB limit on HDIO_GETGEO ?
    ... > sector offset of a hard disk partition. ... I believe GUID Partition Tables (GPTs) are the answer. ... Windows VISTA 64-bit supports GPTs on data disks and new Mac OS based ... systems have been using it on internal drives for a couple years at ...
    (Linux-Kernel)
  • Re: What to do about the 2TB limit on HDIO_GETGEO ?
    ... > sector offset of a hard disk partition. ... I believe GUID Partition Tables (GPTs) are the answer. ... Windows VISTA 64-bit supports GPTs on data disks and new Mac OS based ... systems have been using it on internal drives for a couple years at ...
    (Linux-Kernel)
  • RE: Hard drive noise
    ... Up until I put this new mo-board in the drives were whisper-quiet. ... 'vibrating' problem in one partition, it should be present in others too... ... Under "Standard Dual Channel PCI IDE Controller" ... Device Manager shows driver files ATAPI.SYS, PCIIDE.SYS and PCIIDEX.SYS, ...
    (microsoft.public.windowsxp.perform_maintain)