Can someone give explanation of RAID?

[skybolt_1]

Hey everyone, I'm not having a lot of luck in finding out what exactly these things do. All i know is that RAID stands for Redundent Array of Inexpensive Disks. Could someone give me an explanation or a link to one? Thanks.

[Fingers]

Read this: http://sysopt.earthweb.com/forum/smile.gif http://sysopt.earthweb.com/forum/Forum1/HTML/007859.html

[Richard_Cranium72]

A mobo or i/o card that will support multiple hard drives, known as RAID->>

Will allow multiple HD's to access and write info at the same time, minimizing the risk of loss of data while giving the capability of a SERIOUS increse of transfer rate.

RAID is much quicker than a SCSI hd.
Short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance.

RAID disk drives are used frequently on servers but aren't generally necessary for personal computers.

There are number of different RAID levels. The three most common are 0, 3, and 5:

Level 0: Provides data striping (spreading out blocks of each file across multiple disks) but no redundancy. This improves performance but does not deliver fault tolerance.

Level 1: Provides disk mirroring.

Level 3: Same as Level 0, but also reserves one dedicated disk for error correction data. It provides good performance and some level of fault tolerance.

Level 5: Provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance


link to several mfg pages->> http://www.computerhope.com/hdspecs.htm

webopedia->> http://webopedia.internet.com/

glossary of computer terms->> http://homepages.enterprise.net/jenko/Glossary/G.htm

DrVette

[qball]

DH,


RAID is much quicker than a SCSI hd.


What if you RAID SCSI drives?

Also, even using ATA100 drives, you'll need 3 (maybe 4) drives and a RAID controller to beat a single SCSI U160 Hard Drive. Quicker, yes, but much more expensive also...

So, now when one takes multiple SCSIU160 HDs and then adds a RAID controller, what IDE solution even has a chance....

[Aleph1]

So very true qball....SCSI will always kik IDEs *deleted* . Although, I have to admit, IDE is becoming better and better. Any of you read about the new Quantum Atlas 10k III?....MMMMMMMMM!




[This message has been edited by Mntsnow (edited 10-23-2000).]

[vass0922]

RAID 5 rocks http://sysopt.earthweb.com/forum/smile.gif
Can you say Hotswap?!?! http://sysopt.earthweb.com/forum/smile.gif

[herzogs]

Greetings,

With respect to RAID and speed, it is important to state that the speed gains obtained with RAID are for raw data throughput. You can read 1G of data from a RAID array quicker than you can from a single disk. One gotcha however; the latency of a RAID array is no better than a single disk.

The other major reason people use RAID is to provide failure protection. With RAID 1, 3, 5 and 10, you can loose any single disk, and the RAID group will continue operating without data corruption. When using RAID in this manner, featurs such as hotswap and hotspare may be important. Otherwise, you will need to schedule downtime to replace the defective disk.

It is also important to note however that RAID does not protect you from deleting a file accidentally. If you want to recover a deleted file, daily tape backups are the way to go.

There have been some posts related to the promise fasttrack ata/66 raid card in this and other referenced forums, and I thought I'd add my two cents worth.

The promise card is simply a 2 channel IDE controller with a bios patch that lets the computer CPU do all the raid work. If you have an OS (linux) that ignores your bios, the card simply behaves as a plain IDE controller. In my opinion, this card should be avoided.

There is a great product out from 3ware that provides raid using IDE disks. The card acts like a SCSI card providing caching and limited tag-queueing. (multiple outstanding disk reads and writes can be requested before the previous io operation is complete) The 3ware product starts at around $145 for the two disk version. Details are available at http://www.3ware.com/products/escalade6000.shtml

We recently put together a system for a client who does video editing. The system used 8 IDE disks 40G/7200rpm/2M/ATA66 and the 3ware 6800 raid card in raid 0 mode (striped). The total disk space was 320G and cost lest than $2000. Performance was great, reading 1G files at about 80M/s, and writing at about 75M/s.

Much of the speed gain is only in the area of sustained disk io. The 3ware card obtains this by caching the disk request on the card, and then feeding the requests to multiple disk drives at the same time. Seek time on a raid array is not any faster than a single disk in the array.

The 3ware card also has some optimizations for various raid configurations that the cheaper (promise) cards simply can not do, Such as reordering disk block requests to suit the drives rather than performing the operations in the order the computer requested them.

One thing the 3ware card does not do is raid level 5. Their tech support suggested their next version (7000series?) will support it in Q1-2001. I haven't seen it announced yet.

Adaptec and others make SCSI RAID cards that have all of these features, however these are usually very expensive and are only cost effective in large servers. SCSI usually runs at about twice the price of IDE by the time you add in all the cables and such.

For those on a budget, IDE raid (when done properly) works very well for the money.

Specifically, for home users looking for disk falure protection, using IDE raid 1 (mirroring) is fairly cost effective when compared to tape backup solutions.

Good luck,

Steve


[This message has been edited by herzogs (edited 10-26-2000).]

[Richard_Cranium72]

herzogs !!

You iz da MAN !

If you keep up posts like that,, you and Beemers will be the next inductees into the group of the "OWO" (old Wise Ones).

This group is very elite and secretive, age is of NO concern, some of the OWO members are as young as 14.

Your post has not only met the minimum requirements for nomination to the OWO, but far exceeded them.

A continuation of this type conduct will most assuredly you of a seat on the board.

The completeness of your post, it's veracity, scope, articualtion, comprehensiveness and how it fit into other postees comments were in perfect rhythm to the frequency set on the oscilloscope at the time of your posting.

The OWO panel runs the post through a specially written software to determine the posts cycles per second, yours matched perfectly.

congratulations http://sysopt.earthweb.com/forum/smile.gif

BTW, when you edit a post, you can delete your previous edit.
" [This message has been edited by herzogs (edited 10-26-2000).]"

happy computing,,
DrVette