[ILUG] Hardware RAID & partitions

[Wesley Darlington]

Hi,

On Wed, Feb 02, 2000 at 07:46:33PM -0000, gary mc closkey wrote:
> Hi, here's the sit.rep. ...
> 
> Equipment: Dell Poweredge 2300
>            PERC2/SC RAID Controller
>            4x8.5GB SCSI HD, configured as RAID5
>            RH Linux 6.1, (2.2.12-20) Dell installed
> 
> Problem:
>         the scsi raid array is currently
> configured as /dev/sda1 .. /dev/sda9 .
> /, /home, /boot, /usr, swap, /var and /tmp are
> currently mounted on different partitions. So far
> so good, Except...
> 
> /var is on sda8 and is too small to cope with the
> intended mail & printing files that will be
> generated in /var/spool . /tmp is currently a
> single partition of 17GB.
> 
> I want to give /var more space ,
>  I want to reduce /tmp to something more
> reasonable, and use the remaining space for file
> sharing.
> 
> To my mind, all I need to do is use fdisk to
> delete the /var and /tmp partitions, then recreate
> them with smaller sizes, and then add a new
> partition for the filesharing. Except this is all
> RAID based, and I'm scared that I'm missing a step
> and hence going to fsck things up.
> 
> Please confirm, deny, suggest a better method.
> 
> 
> Addendum: slightly different problem -  /home on sda2 is also probably going
> to be too small at 4GB. Can resizing be done, or will it require a
> re-install?

You have a number of options...

o Buy partition magic for windows. You can then download a binary for linux
  to resize ext2 partitions. I think it's called ext2resize.

o There are a number of other ext2 resizers about - freshmeat.net is your
  friend. Also, the partition magic resizer had a clause that made it become 
  GPLed sometime. That time might be here already.

o Forget about resizing. Go to single user mode, "cp -dpR" the contents of 
  /var to a partition with loads of room. Possibly do same for /tmp. Umount 
  the partitions. Run fdisk. Make new filesystems. 4kb blocksizes for big
  filesystems. Check stri[pd]e size of your raid. See man page for mke2fs. 
  Copy backups back. Triple check /etc/fstab. Enjoy.

o If you're worried about /home being too small, it's a bit of a pain that
  it's near the beginning of the disk. You could just swap /tmp and /home, though
  It'll need some towers-of-hanoi style jiggery-pokery, but you can do it. :-)

o Hardware raid - it's transparent to you. Treat the big raid as one logical
  disk. Just like you would any other *single* disk. There's nothing magical
  here. That's why linux calls it "sda".

o If you /are/ reinstalling, consider raid 1. Keep, say, /home on one raid
  1 array and everything else on another. With swap on both. Me, I *despise*
  raid 5 for its awful write performance. Especially on the controller you have.
  Benchmark. Disks are (relatively) cheap.

o I think the megaraid driver presents multiple logical drives to linux as
  LUNs. So, you need to enable "probe multiple LUNs" in your kernel, if it
  isn't already enabled. (That is, if you eschew raid 5. :-)

All the best,
Wesley.