RAID1 on computer w 2 internal hard-disks

Question

I would like to hear from people who configured a computer with these properties:

1) The computer has exactly 2 identical hard-disks, i.e. no additional internal hard-drives are available. There is CD/DVD drive and USB.

2) The 2 disks, or their portions, are in RAID-1 array.

3) The OS is Win XP or Linux. I am interested in solution for both OSes, but each machine is single-OS (no dual-booting).

I have had several such boxes and laptops. I used on-board INTEL RAID support, HiPoint sw-based (fake-RAID) PCI controller and an Adaptec PCI controller. Overall I had OK results, but I did face these hassles:

a) Upgrading LINUX kernel on a machine where one boots from RAID-1 was major pain. It took me several painful long days to get it done, later I was reluctant to do kernel upgrades because of this.

b) When doing backups and/or partition management, one has to have a tool that can deal with the RAID. I use Acronis True Image; Acronis support recommends using the Live Bart PE CD to load the RAID driver, in place of the Acronis bootable CD implying that backing up a bootable RAID-1 partition is an "advanced" task with Acronis.

c) On laptops and often also on desktops I have no PCI slots available, if I wanted to buy a quality hw RAID card, I have no slot to install it in. So the choices are often sw raid or BIOS-level on-board RAID.

Quite often I hear a recommendation of creating a non-RAID boot-partition. How large should this partition be? Is the info on this partition read-only? Is the info on such partition accessed by the OS only during boot or also after boot is complete, during normal operation? I reboot my machines only once every few months, I do not mind a slower boot process if I gain in simplicity / robustness.

Does anybody have 2-disk boxes with RAID-1 that they are happy with?

TIA, Radim

Answer 1

I'm happy with mine. I actually have 4 identical 1TB disks.

First 2 are in Raid 1 - on those I install Windows (7) and all software and store all documents.

Second 2 are in Raid 0 for speed - on those I install all non-critical stuff - games, video, music.

I also set it up to have the windows temp folder on the Raid 0 drives.

Raid setup is all done through Intel Matrix Raid in bios on a Gigabyte P45-DS4P.

Answer 2

If you have a decent raid card then you don't need OS drivers, it presents the array as a single scsi disk.

Also I question that you are actually using RAID1 appropriately if you want it in laptops, etc. It is not a substitute for backup.

Answer 3

2-disk RAID 1 works fine, but the onboard fake/SW RAID solutions are best avoided. There are onboard hardware RAID on some (quite expensive) mobos that are fine. If no real onboard hardware RAID, adding a card is the only way (that I can think of at the moment) to do it right...

Answer 4

Upgrading LINUX kernel on a machine where one boots from RAID-1 was major pain. It took me several painful long days to get it done, later I was reluctant to do kernel upgrades because of this.

You're doing something wrong. The components of a linux software RAID-1 are readable separately. As long as you compile md support into the kernel and use grub as a bootloader you shouldn't have a problem.

My desktop configuration has an 8 disk RAID-6 with a separate RAID-1 /boot. Each disk has a 100M boot partition, a several GB raided swap partition, and the rest of the disk as a large raid partition. All three partitions are of type linux raid.

The /boot partition has a grub install and is RAID-1 across all disks, with grub installed to the MBR of all disks. This means I can boot off of any of the disks.

Swap doesn't have to be RAID, but if it isn't you'll be in a bad spot if a disk fails. The swap space also gives you a bit of flexibility if you need to replace a disk with a slightly smaller disk.

The rest of the disk is a physical volume for LVM. (or, if you prefer, several separate RAIDs and no LVM) There are logical volumes for /, /home, /usr, etc... whatever partition configuration you prefer.