What is RAID?

[crspii]

http://www.pcstats.com/articleview.cfm?articleid=830&page=1

haha that link has a funny picture.

RAID is not bug spray...








... or is it?

 

[crspii]

so can u have say... two 80 gig hdds with striped raid 0, and one 160 gig hdd mirroring all of it.. that way u dont need 4 for raid 0+1?

 

[asupertech]

but its funny and ironic that after i asked that, u not only gave me a long answer but it was not answering the question.

lol the sign of a good politician maybe?? lol

And as you see from the Picture Raid stands for R..A.. of Inexpensive Disks... Inexpensive whas the term they used when Large drives were very expensive, then they changed it to Reduntant array of Independant Disks.. but that is nerither here nor there...

so that link you posted was a great link.. to learn about RAID 0, 1 and 0+1 levels.

and now i will try to give you the answer you seek....
Basically there are 5 levels of RAID. Well there are more, but you wont need to know more then the 5 basic levels.
read this link it provides a quick desription.
http://www.win2000mag.com/Articles/Index.cfm?ArticleID=218

this one is a little easier to understand
http://www.systemlogic.net/articles/01/1/raid/page6.php

I have never needed to use level 2, 3, or 4 for any practical application. 5 is what i recomend if you are going for both performace and total size. But you will need a (hardware) RAID controller.

First and foremost, RAID is NOT for backup.. at any level, it is mearly for redundancy... your backup program is for backup..Each level of Raid provides a different level of redundencey and performance.

RAID 0 can combine two hard drives into one using striping, and greatly increase the speed that the drives transfer data.
*****There is no fault tolerance

RAID 1 in the event of the failure of one drive, the other can be substituted (most of the time) data can be read from both drives simultaneously, increasing the speed of data retrieval Write time is the same.

disadvantage of RAID 1 a mirrored array can use only half total amount of the two disks combined. 2 10 gig drive provide only 10 gigs of space.


RAID 1+ 0 requires a minimum of four physical drive. two pairs of striped drives are mirrored together
disk space again s opnly half of the total amount. $ 10 gig dives yeilds 20 gigs of space.
advantage : any failed drives can be swapped out for new ones on the fly

Raid 5 requires a minimum of 3 Disk drives. this provides parity to your RAID. you get 2/3 of the amount of space available. 3 10 gig drive allows for 20 gigs of space. the thris 10 gig is the parity. it is the best combination of performance, redundancy, and storage efficiency.

Ok OK i know, my answers are long and drawn out sometimes...

 

[asupertech]

so can u have say... two 80 gig hdds with striped raid 0, and one 160 gig hdd mirroring all of it.. that way u dont need 4 for raid 0+1?

short answer..... no

 

[crspii]

lol the sign of a good politician maybe?? lol

Raid 5 requires a minimum of 3 Disk drives. this provides parity to your RAID. you get 2/3 of the amount of space available. 3 10 gig drive allows for 20 gigs of space. the thris 10 gig is the parity. it is the best combination of performance, redundancy, and storage efficiency.

Ok OK i know, my answers are long and drawn out sometimes...

HAHA. good politician. more like... typical politician. . that was a good one.

so wait... RAID 5 from ur description sounds a lot like taht little plan i had... i'll believe u when u say it wouldnt work, but meh, just seems similar.

so this fault tolerance thing is basically the array's ability to have HDD failure / error ?

wat is the difference between SATA- serial ATA and just plain ATA? i keep seeing that mentioned.

and is an ATA/100mb/s good speed for a RAID system?

 

[cheerios]

hmm so physical raid depends on the mobo? and not on the hdd? hmm i always tot it was the other way ard

btw nice sites

 

[asupertech]

HAHA. good politician. more like... typical politician. . that was a good one.

so wait... RAID 5 from ur description sounds a lot like taht little plan i had... i'll believe u when u say it wouldnt work, but meh, just seems similar.

you can use those three drives, BUT, you have to have 3 or more partitions or equal size to create RAID 5. usually you would use the entire drive, not partion it to make the right size.
Take 3 10 gig drives
the three are "striped" togther to give you a net size of 20 gigs.

the reason you use three drive is that if one fails, The "striping" (that is the parity) allows for the raid to rebuild itself when you put in a new 10 gig drive, that is where the redundency comes from.

if you use, from your example... 2 80 gig drives and one 160 gig drive. you will only use
drive 1 80 gigs; Drive 2 80 gig; Drive 3 80 gigs.

will give you a net size of 160 gigs of usable space. you would waste the other half of the 160 gig drive. reason, say it is the 80gig partiton on the 160 gig drive that fails, you have to replace the entire drive, if you had something on the other half of the drive, say you made a secondary partion, what ever is there is now gone...

Originally posted by crspii
so this fault tolerance thing is basically the array's ability to have HDD failure / error ?

exactly, so if one of your drives fail... on the fly(if you have hot swap drive) you pull the bad one out, replace it with an exect size drive, the raid rebuilds itself,
you users don't even feel a thing, all is well in the world..

without fault tollarance:
A drive fails...system shuts down, you lose data, you replce drive, you restore from backup... you users are very unhappy... boss yells at you, you make excuses.....

Raid also provides better overall performace from the drives

Originally posted by cheerios
hmm so physical raid depends on the mobo? and not on the hdd? hmm i always tot it was the other way ard

NO. Physical (Really HARDWARE) Raid depends on the Raid controller you install ON the motherboard, usually into a PCI slot.
the HDDs are just a part of the RAID..
the only thing raid controllers care about is if you have:
3 or more of the exact size drive to make RAID 5.
2 of the exact size if you want to make Raid 0
4 or the exact size if you want to make Raid 0+1

Some mother boards do have built in Raid controllers, but they are far less effective to Add-on Raid controller cards... (usually)

 

[Apokalipse]

neh 1800+ doesnt mean that it runs at 1.8ghz, it just simply means that it competes with the 1.8ghz proceesors with intel

yeh i know that im just confused that he said he has an Athlon XP 1800 running at 1800MHZ

SATA is an alternative connection to IDE which are paralell (although I'n not sure why a serial connection is faster than a paralell one) SATA can transfer speeds of 150MB per second (theoretically) and normal ATA has a maximum of 133MB per second

 

[crspii]

i get raid 0 and 1 but beyond that, im kinda confused. not lost, just confused. basically i want striped-ness and also some fault tolerance, which would u recommend most? (mind u of my budget)

 

[cheerios]

hmm my preference is raid 0 since its for personal use and i have a tight budget i dunno about the rest since Ive only been reading up on raio 0 and 1 haha