Does RAID1 offer a perforamnce increase?

matthew2456 · 11 Feb 2009 at 19:31

Seen conflicting reports on performance increases and the actual reliability,

I will be using motherboard built in RAID

njj1046 · 11 Feb 2009 at 20:03

Have a read of this post by NathanE... http://forums.overclockers.co.uk/showpost.php?p=13454786&postcount=18

Rabtech · 11 Feb 2009 at 20:08

No I would say, in fact you might get a slight performance hit compared to running the drives 'singly' depending on the RAID controller.

matthew2456 · 11 Feb 2009 at 21:13

looks like it'll be a suck it and see!

NathanE · 12 Feb 2009 at 10:43

I have RAID1 on my home and work PC. I'd never go back now. If you multitask heavily it's one of the best and easiest RAIDs to get working for this.

garylouden · 12 Feb 2009 at 11:54

If I remember correctly Raid1 will give you double the performance in read and the same performance in writing.

Rabtech · 12 Feb 2009 at 12:59

After reading NathanE's thread and the document posted above, The RAID 1 implementation in Intel controllers reads are balanced based on disk load - however all this means in normal terms to me is that is just picks the drive to read from that isn't busy.

In a multitasking environment you may see slight increases in disk access speed but it still wont read faster than from the maximum transfer rate of a single drive (ala RAID 0 striping).

I must admit I'm quite impressed with intels implementation of RAID 1 and will probably go back to using it myself shortly. However I bet other 'software' RAID solutions out there dont do this.

Bottom line is dont expect a RAID 0 type speed increase, although multitasking (multiple disk reads) might be a little quicker on an Intel Controller

NathanE · 12 Feb 2009 at 13:46

RAID1 does not increase throughput in general - although it can in certain situations but these are quite rare on a desktop/workstation PC. RAID1 is more about increasing the systems ability to handle multiple read requests.

It is very useful if perhaps you have someone in the other room streaming a 1080p video from you, whilst you are perhaps loading/playing a game or indeed watching another 1080p video from the same RAID array. Because the system can choose which disk is better suited to servicing the read request at that point in time (i.e. by comparing the disk head position against the sector to be read); the disk that can more quickly respond to the request is selected and the read command is then sent to that disk. Leaving the other disk untouched and able to serve other requests, concurrently.

It's a bit like the improvement that dual core/dual CPUs brings really. Not necessarily faster in a single thread of execution, but faster overall in multitasking.

gordan · 13 Feb 2009 at 16:54

RAID1 will effectively double your I/O ops/sec theoretical maximum. For sequential reads, it will make no difference at all. The reason for this is that if you are alternating read operations between two drives, the disk will be read-aheading the data that you didn't (and will not) ask of it, because you asked for it off the second disk. So in long sequential reads, your performance will be the same as a single disk. For writes the performance will be negligibly lower than for a single disk if you have NCQ. For small (up to multi-sector capability of the disk, typically 16 sectors, 8KB) random reads with full NCQ support you will see the throughput roughly double with RAID1.

In other words - RAID1 has the potential to be a lot faster, but it depends on your usage pattern.