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Old 07-21-2005, 01:44 PM   #1
linuxhippy
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optimizing drive speed with raid


I have my FC4 installation on 2 harddrives (hda has my home partition and hdb has the rest). This way I have 10 GB of space. I was told I could optimize my drive speeds by putting each drive on a different IDE channel and using raid. How do you set up raid?
 
Old 07-21-2005, 02:36 PM   #2
michaelsanford
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How do I set up raid. Why not just ask how to write a kernel from scratch :P j/k RAID can be quite comlpicated to get to work properly.

I'm not versed on the way the Fedora installer handles it, so I won't speak to that, I'll just give you some general information.

For speeding up data access you'll want to use RAID 1. This size is a great guide to Raidlevels http://www.acnc.com/04_01_01.html

RAID 1 will stripe data across both drives. If you want speed increase I'd go with RAID 1, if you're looking for fault tolerance you can go with RAID 0.

Now, since you only have 5 GB drives I assume you're running a desktop machine and not a server ? What is the system ? Are you running dual 64 bit processors or an old clunky Pentium II ? How much RAM do you have ? Can your hard disk controller perform two concurrent read operations ? If not, RAID is essentially useless becasue it will have to read from one drive and then the other, but you want to read from both at the same time to get any performance increase.

Unless you have a hefty system you probably won't notice much if any speed increase from the RAID. Remember, RAID only has to do with how data is stored on the hard disks and as such, will only speed up disk access (or in the case of RAID 0 provide redundancy in case of data loss). It won't increase the efficiency of computations per se.

PS It's basically a choice: do you want the headache of trying RAID or not? Here's an example of what's in store (though this guide's for Slackware):
http://slacksite.com/slackware/raid.html

PPS This post all has to do with software RAID. If you want hardware RAID (i.e., you go and buy a RAID controller card) it will be very simple to set and faster since the controller card can read from multiple disks simultaneously (that's what it's designed to do in the first place) but not free...far, far from free

Last edited by michaelsanford; 07-21-2005 at 02:38 PM.
 
Old 07-21-2005, 05:10 PM   #3
linuxhippy
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RAID1 does sound like what I want. My pc is a home pc-600 MHz/P3/320 MB RAM/Promise ULTRA100TX2 PCI IDE RAID card. My first hd is a 6 GB ATA33 drive and my second hd is a 4 GB ATA66 drive.

Last edited by linuxhippy; 07-21-2005 at 05:12 PM.
 
Old 07-21-2005, 05:40 PM   #4
snarkout
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Raid 0 = striping. No redundancy, moderate to good speed gains.
RAID 1 = mirroring. Total redundancy, including errors. Possible read gains.

Software raid uses your CPU, and requires understanding what you are doing. If you choose to stripe (I NEVER recommend that people do - I think it's very risky for not much return) you will be hitting your CPU pretty hard, and if you are running 10 gigs of drive, I'm guessing that your cpu isn't a screamer. It's also going to hammer your IDE controller. I'd imagine you are looking at a wash as far as speed goes, and inviting a lot of risk. Mirroring is a good idea, but will also hammer your CPU and IDE conrtoller. Writes will be the same or slower, reads will be faster, but probably not much. You also cut your effective drive space in half. You do, however, have good redundancy. Software raid can be OK if you have a PCI IDE or SATA card, and have hardware that can handle it. On older hardware, trying to use your IDE controller, you are probably not going to be happy with the results (IMO).
 
Old 07-21-2005, 11:31 PM   #5
michaelsanford
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linuxhippy I'm not 100% certain about this but I think both drives need to be identical (size).
 
Old 07-22-2005, 04:59 AM   #6
linuxhippy
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RAID isn't for this slow pc-thanx for the input!
 
  


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