Ubuntu Server Hotswap RAID 1: Hardware or Software?

I'm building new servers for a project I'm working on. They will all run Ubuntu Server x64 (10.04 soon) and require a RAID 1 hotswap configuration (just two drives) to minimize downtime.

I'm not worried about Raid performance. The server hardware will have plenty of CPU power, and I'm only doing a RAID 1. My only requirements are:

1. Everything, including the OS, must be mirrored.


2. There must be no down-time when a drive fails. I need to be able to swap out the failed drive with another and have the RAID rebuild itself automatically (or maybe by running a simple script).

I'm wondering if the built-in Ubuntu Software RAID can handle this, particularly the hotswap part. 10.04 looks promising.

I'm considering buying the 3Ware 9650SE-2LP-SGL RAID controller, but with the number of servers we're purchasing, that would increase the total price quite a bit.

Any advice at all would be appreciated. Thank you.

Answer

I have hot swapped drives using the software RAID builtin into the Linux kernel on many occasions. You may need to run a command to add the new device. I believe it is possible to make it automatic, but in the places where I use it manually running the command to add the new drive has never been a problem.

I am not entirely certain that the computer will survive with zero downtime. That may depend on your hard drive controller and how it responds to a drive failure.