Re: HOWTO - Speed up IDE HD's
On Sat, Feb 07, 2004 at 11:32:55PM -0800, Roger Chrisman wrote:
> > fun stuff
>
> RAID 1 is one strategy for getting 'faster' read going.
>
> Redundant Array of Inexpensive Devices (RAID) comes in various flavors.
>
> RAID 1 is a flavor where you take two disks of the same size and have the
> computer treat them as one disk. The computer mirrors the identical data onto
> both disks and can read one part of a file from one drive simultaneously as
> it reads the other part of the file from the other drive. Thus reading the
> whole file in half (roughly half I think) the time it would take to read the
> whole file from one drive.
>
> Of course rather than paying for two drives, you might want to just pay for
> one faster drive, more RAM, or some other speed enhancer. If you already have
> the drives sitting around thought, RAID 1 is something you might like.
>
> Linux can do Software Raid. So you do not need to buy special hardware
> controllers.
>
> If you do Software Raid, to achieve the speed advantage you should put the two
> disks that make up your one logical device on separate cables.
>
> md0 stands for 'zeroeth (1st) multiple device,' a notional drive made up of
> more than one real drives.
>
> I did Software RAID 1 with two drives and SuSE 9's Installer for my desktop
> box (just before converting to the Debian way :-). It was kinda tricky. I
> actually bought a 2 Channel Controller PCI card so that I could have four
> total (including the two on my mother board) channels and thus not have more
> than one drive per cable. I have four drives you see. CD drive, back up IDE
> hard drive, and two IDE drives as my RAID 1 md0.
>
> These fancy tricks might not be worth it though if your system bus is 33MHz.
> My two PIII servers have 33MHz system bus (PCI host bridge). So I don't think
> it would be worth the trouble on my servers.
>
> Someone who knows more about RAID please tell me if I am mistaken about that.
Oh, I think it'll be useful. Remember, PCI at 32bits and 33Mhz can transfer
132MBytes/sec, and your drives won't fill that up. Also, once you start
seeking, your disk throughput goes down radically.
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