23 December 2010

RAID 0 vs. RAID 1 on AMD SB770 motherboard chipset

Few weeks ago I've installed second hard drive into my home PC and configured RAID 1 with using motherboard chipset (AMD SB770). I can't say that I saw some real performance boost. PC was working as usual. I think boost had place, but it had totally psychological nature and only in my mind. Because 1w ago I tested performance of raid array. So, with 2 disks it gave me 102MB/sec avg read speed (I used HD Tune). I removed 1 disk from array - It's RAID 1, I can do that! :) And tested again... Wow! 100MB/sec! Second disc gives nothing. Only second copy of data. It doesn't speed up disk subsystem.

I read a lot about RAID arrays, types, reliability, performance. And found that not all RAID 1 implementations do distributed read requests in order to increase read speed. The main idea of RAID 1 is redundancy. So, my motherboard's chipset supports RAID 1. It just supports it. Only essential functions. There is no double read speed. Probably other vendors implement this feature, but not AMD.

Today I've tried RAID 0. In short words it gives significant speed up according to HD Tune. Average speed of read is 216MB/sec. It's just benchmark, let's see how it performs on home PC. And yes, I know that my data is under double risk now :)

P.S. I can't get rid of idea of buying discrete sata raid controller.
P.S.S. During usage of RAID 1 I've found that Linux sees raid as 2 separated disks: sda & sdb (at least Gentoo Linux from installation CD). I think it requires proprietary drivers.


  1. I think you have only simply soft raid controller - and linux see real hardware. Or you have specification for this chipset?

  2. No, I didn't find specification :) As far as I understand I have just SATA controller with implementation of RAID functions in OS drivers. Right?
    Ok, but question: why RAID 1 implementation doesn't contain stripe read in order to increase data transfer rate? Is it because of lazy programmers in AMD or there is some real limitations? According to wiki RAID 1 should increase data read rate.
    And following: What is the sense of "RAID Mode" setting in BIOS for hard drives? I think it just tells to firmware/drivers which contain RAID implementation to turn RAID on. It looks a bit ugly.

  3. BTW Denis, did you try these firmware RAIDs with Linux?

  4. I have one motherboard with soft raid - on linux determinate as simple SATA controller. And i have only one HD, and not run any speed test. Additional firmware for this controller VIA not released.