Re: RAID

[lsorense@csclub.uwaterloo.ca (Lennart Sorensen)]

On Thu, Nov 10, 2005 at 11:30:51AM -0800, lordSauron wrote:
> On 11/10/05, Albert Dengg <a_d@gmx.at> wrote:
> > see http://en.wikipedia.org/wiki/Redundant_Array_of_Independent_Disks
> 
> I just got to read that most excellent article and it raised one
> question about the theoretical configuration:
> 
> RAID 1 or 0?  It said that 0+1 would mirror two RAID 0 arrays - very
> useful, if I only had 4 disks...  So, since I'm only getting two, I
> just wondered whether RAID 1 really has the ability to give
> performance increase similar to RAID 0.  Since I'm going to get two 80
> Gb SATA150s, I  don't want to sacrifice performance, since eventually
> the machine will become my webserver (yay!) though I'm still not sure
> I'll need that much performance... but nevertheless it doesn't hurt to
> be prepared.
> 
> So in more clear and less confused words, does RAID 1 really share the
> advantages in speed of RAID 0?  I'm just a little skeptical, and I'd
> like to know if there's any testimonies of people that have actually
> had the chance to find out.

raid1 has the same performance as a single disk, but with added
reliability since you store identical data on both.  now a web server
probably doesn't need more speed than the single disk or raid1 can give
since the bottleneck is almost always the network link, and not disk
speed, or sometimes the cpu if you are doing a lot of scripting.

Even on a fileserver it is becoming hard to have your network link
outperform your disk IO unless you have a very good gigabit or better
network link.  Any single modern disk can saturate a 100Mbit link.

Len Sorensen