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The Pros and Cons of RAID Level 1 Posted April 2, 2002 EST 10:55PM by Agitator!!

Ever since I installed a new motherboard with an onboard RAID controller, I've been debating whether to use that controller to do Level 1 RAID (Mirroring, real-time duplication of the main drive) or just use the second hard drive for weekly backups. So I did a little research and the result of that work is The Pros and Cons of RAID Level 1.
    For many years, I used tape drives to backup my PC. However, as time went by, I would have to keep buying larger tape drives to keep up with the sheer volume of data on my hard drive. Eventually, my diligent backing up slacked off as more and more tapes were required to complete a single backup. Occasionally I would make a Ghost image of my drive, but I did it so infrequently, it was hardly a reliable backup. In the end, I gave up data security altogether by having no backups. As I was planning my next upgrade, I read an article in MaximumPC magazine that recommended buying a motherboard with a built-in hardware RAID controller. Their position was that even if you didn't use the RAID capabilities, you could still split your IDE drives on to separate RAID channels. If you had four IDE devices, each would have its own IDE channel, thus minimizing traffic on each channel. So I paid the extra and purchased the Abit KR7A-RAID motherboard.
The article goes on to discuss things like improved read times versus slower write speeds. To read more, click here. I hope you find it informative.

Name: Bryce
Date: February 28, 2003 EST 12:31AM
Comment: If your going to use a RAID config on your primary system I recomend a RAID1 or RAID5. Just backup your system to another harddrive once ina while. i would also have to say that SCSI is the way to go if you have the cash.

Name: Zobadak
Date: January 21, 2003 EST 12:16PM
Comment: Rather off base for your use of RAID 1. RAID is for the protection of your data not the OS. To address this efficiently within the scope of your document you would have three drives. Drive one is for Operating System only and would hang off the standard IDE controller. The second and third drives would be a mirrored configuration hanging off the IDE RAID Controller, one drive on each channel to maximize the read/write times.

If you maintain a base image of the OS drive from time to time a rebuild of drive one is easy via restore/ghost of OS image. Data on the RAID drives is never affected by the OS drive or its potential corruption.

Name: ricky037
Date: December 23, 2002 EST 10:05AM
Comment: Good reading. I too run some "Fault Tolerance" on my system by partitioning the HDD with a OS/System drive and DATA drive. Then create a image of the OS/System drive and putting the image directly on the DATA drive. (RAID1) When it fail. (And it did) I just pop in a new drive and a floopy and the system is back up in about 30 mins.

Name: Agi
Date: August 17, 2002 EDT 12:22PM
Comment: Yea, it's does appear to be a contradiction, but it really isn't. RAID 1's greatest strength is realtime data backup. Assuming you don't screw around with the system, then RAID 1 can be very beneficial.

Name: Rich
Date: August 6, 2002 EDT 11:05AM
Comment: In your article under "Realtime data security" you say both drives are corrupt, But in "Final Thoughts" you controdict the above ???

Name: Sam Vilain
Date: July 17, 2002 EDT 9:23AM
Comment: RAID 1 normally does not slow down writes; the writes may execute in parallel. Only with crap hardware (eg, two IDE drives on the same controller, or software RAID + IDE) is the double writing load an issue. The effect is barely measurable even when mirror is performed in software when using SCSI hard drives. If you don't believe me, benchmark it.

Also, for random access RAID 0 *increases* the total number of I/O requests for a given set of work, which may in some cases slow the system down. This is because most of the time the limit on system performance is not the burst rate, but the number of I/O requests per second - modern disks can not do all that many more I/O requests per seconds than 10 year old disks; this certainly hasn't increased with Moore's Law.

This is why the biggest and high performance databases in the world use only disk mirroring, and NOT RAID 0/5.

Name: Genghis
Date: July 7, 2002 EDT 8:48AM
Comment: I have a client who wanted a RAID 1 solution. They were paranoid about redundancy and work on a 3 drive system. 2 drives in the system and the 3rd disc swaps with the second one every week so they have a complete backup off site that is a exact replica of the system incase of a major problem. So all they need to do is throw the good disk back in and they are 90% of the way to be running again.

Name: john fisher
Date: June 26, 2002 EDT 6:50PM
Comment: As stated above, secondary backups in addition to the mirrored data are also necessary. My approach is to partition (or use another drive) to separate the OS/Programs from the data. I image the OS and back up the data as necessary. Mirroring the data partitions seems like a good idea. I'm looking into the RAID1 software NAS solution (STORaid).

Name: XJK
Date: June 17, 2002 EDT 8:30PM
Comment: How do you figure that you don't have as much space? You said "Less storage space - For example, with two 60GB drives, the total usable storage space is 60GB and not 120GB". That is not true! wow??!??

Name: Mike
Date: April 5, 2002 EST 3:48PM
Comment: A short, simple article that nicely summarizes on-board RAID. I'd recommend that anyone unfamiliar with the concept read this article before buying a new motherboard with RAID.

Name: whanafi
Date: April 4, 2002 EST 1:50AM
Comment: I use a Gigabyte GA-8IRXP motherboard with a Promise RAID controller built in. I have had similar experience with the data size overwhelming the backup device and so decided to put a pair of Maxtor D740X 80Gb drives on the RAID controller as my data drive. I don't worry about screwing up the primary, because I use Drive Image to store the backup on the RAID. Keep your primary as a single system disk, and use the RAID for storage/backup.

Name: Joe
Date: April 3, 2002 EST 8:35PM
Comment: Raid 1 doesn't provide "Data Security", it introduces a level of "Fault Tolerance".

The term security is used in conjunction with access controls (like file permissions, encryption, authentication, etc)

Name: Millsy
Date: April 3, 2002 EST 5:55PM
Comment: The only problem i know of with Promise Raid, is that it is software raid, and not Truly independant of the OS. I have a promise Raid Controler in a RAID 0 with dual 40gb MAxtors on it. I had to get a new hard drive to install linux on. Because linux couldn't use the controler correctly. I don't know if this is the case for the on board raid..

Name: Jon
Date: April 3, 2002 EST 6:35AM
Comment: Good read. Its important to note as you did that raid1 isnt designed to stop user cockups its designed to minimise down time and loses with hardware faliure. Raid1 should not replace backing up, it should complement it in a mission crictical server

Name: Mungler
Date: April 3, 2002 EST 6:28AM
Comment: the fact that mirroring, whilst creating an exact backup, also duplicates the errors, is a very important point, I used to have a motherboard with onboard raid on it, but I never used it for that exact reason, if you torch your primary drive, the secondary will be an exact copy of that. not really that useful when you think about it. I have stick with regular ghost backups to my second drive. simpler and easier.

Name: doesnt
Date: April 3, 2002 EST 2:03AM
Comment: good read, simple and clean. important with today's abundance of onboard RAID.

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