Software Raid1 demand

Question: How much is the performance of computer affected if I were to use software raid (1) in Linux?

Computer:
2.66 Ghz Dual Core
2GB ram
300GB, 500 GB, 500 GB hard drives (7200 rpm each)
Intel® Desktop Board DQ965GF

I'll be running simulations which involves fair deal of reading from and writing to drives, in addition to CPU usage. I'd like to make sure that performance wouldn't be affected considerably if I were to use softraid in Linux.

Thanks in advance.

Software RAID0 and RAID1 do not use any meaningful CPU cycles. Its RAID5/6 that really "uses" your CPU as something that exceeds 1% usage.

However, the performance of most RAID1's is that of a single drive, no more. I would be keen to test this on Linux though.

You've seen software RAID5 on windows probably, with awful performance. If you look at smarter designs on Linux/BSD you will see it uses more CPU cycles but has much higher I/O performance. For soft RAID5 on windows, the only driver that does I/O combining is the Intel ICHxR driver, and its not even that fast in RAID5. While in BSD its possible to exceed 400-500MB/s write speed with sufficient disks and CPU/memory speeds, as memorybandwidth is the likely bottleneck here.

Simple RAID5 drivers on windows don't implement writeback aka buffering. Without this they are unable to combine and split I/O which is required to make a fast RAID5 driver. Implementing all this in software will make a complex driver though, certainly not as easy as a RAID0 or RAID1. That's probably the reason there is no real "proper" RAID5 driver on Windows.