RAID - Migrating from single to RAID and back again ?

[Defenestration]

This is a question that fits into both the motherboared section and the HD section, so I picked HD

I have no experience with RAID and am looking to get an Asus P5B Deluxe motherboard with a Samsung Spinpoint 250GB hard drive. Later on I may wish to add another 1 or 2 Samsung's and switch to RAID 0, 1, 5 or 10 .

After adding the drives, how would I go about utilising the extra drives in my specified RAID config (eg. do I just change a BIOS setting, and then let it migrate automatically ?) ?

Suppose, I wished to migrate the RAID setup back to a single drive at a later date. How would I go go about doing this ?

Also, what happens when one of the drives in a RAID config fails (eg. will I get a BIOS error on boot ? What happens if the drive fails while in Windows ? ) ?

 

[rpstewart]

Online RAID migrations can be a bit tricky, I know it can be done on NForce4 based SATA controllers but I'm not sure if the Intel Matrix RAID can do it. I would be surprised if it couldn't but I can't find anything to hand which confirms that.

It may well be easier to wipe the disks and recreate the array(s) from scratch each time.

In theory, however, what you need to do is initially create a single disk RAID0 array and then install Windows as normal using the RAID drivers. When you add more disks you should be able to use the RAID management utility to bring it/them into the array. You should be aware, however, that you'll still need to use something like Partition Magic to expand your partition(s) into the new space. There are also limits on what level migrations can be done online, you may not be able to go from RAID0 to RAID1 or RAID1 to RAID5.

RAID5 isn't something you should consider as your only array, the performance of mobo based RAID5 is too slow for normal use really. Reads are quick but there's a huge CPU overhead associated with writes and the speed ends up being very poor in comparison to a single drive, this makes any paging operations very slow so task switching will be painful.

You can't remove disks and automatically migrate back to lower RAID levels or smaller arrays. Doing that is a wipe and start again job.

If a drive dies (or just hiccups at boot) the message will be dependant on the RAID level and the time of failure. At boot time you'll get a BIOS message, for RAID1 and RAID5 you'll be given the option to attempt an online rebuild there and then or you can carry on with a degraded array. Both will allow you to continue to Windows. If RAID1 or RAID5 fail in Windows then you'll get a similar message but that'll be a rare occurrence, the vast majority of HDD failures occur at boot. For RAID0 it's a different story, at boot you'll get a message but there's very little you can do, the data is probably lost. In Windows it's just like a normal HDD fail, Windows will hang and you'll get an error when you restart.

 

[JayMax]

Can't really add to rpstewarts usual high quality post, but here is a list of supported migrations using the Windows management software:

http://www.intel.com/support/chipsets/imsm/sb/CS-020674.htm

You're generally looking at Ghost or Acronis if you're going to reconfigure arrays frequently - e.g. I'm currently running a 3 disk Raid 0 array, to add a fourth disk (in Raid 0) I'll have to image my os, rebuild the array, then restore the image.