Raid

[canadian_divx]

i may seem like a moron for asking this but what is it and how would it help, my friend talkes about it booting up faster with it but that dues not help me because i never shutdown unless it is a new instaltion of software, but can you take the raid ports and just have 4 hdds on them and then with the other ment for the cd-roms and stuff can i use thoes too at the same time

totaling about 6hdd nad 2 rom (dvd and cdr)
2 raid ports and anouther 2 IDE ports???
is it possable or what?? is it worth the extra cash??

 

[dreamliner77]

yes it is possible and I believe it's worth it. If I build a high quality machine for friend or something, I use one of these boards so each IDE device is on it's own channel

 

[canadian_divx]

if there are 2 80gb westwendigital drives on the same channel and they are both 7200rpm, will it affect performance if they are one there own or is it just then there is a differnece between like a 7200rpm and a 5400rpm???

 

[ditchhopper]

Raid doesnt make your machine boot faster. It actually takes longer for a raided pc to boot since it has to also load your raid/ata software at startup. However, once your runnin you increase your hdd access speed for every drive you add to the array using raid 0. Raid 0 stripes your drives for performance while Raid 1 mirrors them for security. You can also combine them to get Raid 0+1 which does both. Example: If you used your 2 80 gigs in a 0 stripe you would have 1 160 gig drive that was twice as fast because both drives are reading and writing different parts of a program. Those same drives in a 1 mirrored array
will also give you 160 gigs but no faster than 1 drive because they both contain the same information. If one drive ever fails you can replace it and data off the other one will be written to it.
For raid 0+1 you need at least 3 hdds. I run raid 0 on 4 seperate drives for my game server. Works great but you have to remember to backup, backup, backup. Although I should add I havnt lost a drive yet. Good luck.

 

[ditchhopper]

Forgot to add that your other alternative is to just use your raid controller as another ata device. No speed or security, you just get to hook up 4 more devices.

 

[GraveLayer]

I was running a fancy SCSI Raid setup and now just went to 1 WD 8M cache drive.
To tell you the truth I like the one drive better! Performance is just not a factor! Maybe if I did nothing but video editing but I DON'T!
Then there is the XP raid issue to deal with too!

 

[Zedric]

Originally posted by ditchhopper
[...] Those same drives in a 1 mirrored array
will also give you 160 gigs but no faster than 1 drive because they both contain the same information. [...] For raid 0+1 you need at least 3 hdds.

Nope, RAID 1 will only get you 80 Gigs on two 80 Gig drives. RAID 0+1 will require 4 disks.

 

[ditchhopper]

OOps, thats right. 2 80s does equal 1 80 with raid 1. Thanks Zedric. However, 0+1 does work with a minimum of 3 drives. Ive done it before.

 

[Zedric]

It does? Did you mirror two and stripe them with the third? That seems pretty useless. I can't see any advantages unless you use 4 disks (two striped pairs mirrored).

 

[spikemic]

Originally posted by ditchhopper
Those same drives in a 1 mirrored array will also give you 160 gigs but no faster than 1 drive because they both contain the same information.
For raid 0+1 you need at least 3 hdds. I run raid 0 on 4 separate drives for my game server.

this is wrong 2 80 gig drives in raid zero will give 160 gig but only 2 (two) 80 gig drives in raid 1 (mirror) will only yield 80 gig total as is one is just a mirror (copy) of the other

raid 0+1 may work on only 3 but will only yield the size of the smallest drive (and thats all it will use on the others)

example: two 20gig in raid 0 and then mirrored to a 40 gig would use all space but say three 20's (2 in zero and last mirrored) would only give 20 as you could only use 10 gig of first 2 drives to make 20 because thats all you could mirror on the third. ( can get confusing)

to get full use of drives in 0+1 you need 4 matching say 80 gig then you make two raid 0 arrays (yielding 160 gig each) then mirror one array on the other. still only ending up with 160 gig.......

and as far as booting faster, no i don't see it, only way it maybe might is if its a hardware raid (hardware takes care of the raid, not the OS)

 

[ditchhopper]

Thats correct but it is assuming that you are using 0 on 2 drives and the 3rd drive for the mirror. When I did this over a year ago
using 3 drives it worked like this: The 3 drives ALL ran Raid 0 and at the same time they ALL ran Raid 1. The software splits every program in two pieces for the 0 and places the whole program on the 3rd disk. It balances programs across all 3 so that your using all available space. No matter which disk fails one of the other 2 remaining disks has the entire program, either split across the 2 or entirely on the one allowing you to replace the failed drive and rebuild your array. In this case I used 3 40 gigs for a total of 80 gigs. Theoretically twice the speed with the benefit of a mirror. Like you said, if 1 drive is smaller than the other your losing space on the bigger drive(s). I cant remember what raid controller this was ( it was on a friends puter) but I seem to recall it being called Raid 5 instead of 0+1. It worked but we didnt like it and it soon got scrubbed for a 3 disk 0 stripe.

 

[Zedric]

Well that didn't add up...
Btw, RAID 5 and RAID 0+1 are completely different. I suppose I'll throw in my RAID-post again:

Here is "What You Need To Know About RAID".

RAID - Redundant Array of Independant Disks.
There are several types of RAID. Here are the most important.

RAID 0 - Stripe:
======================
Disk 1		Disk 2
------		------
|  1 |		|  2 |
|  3 |		|  4 |
|  5 |		|  6 |
|  7 |		|  8 |
|  9 |		| 10 |
| 11 |		| 12 |
| 13 |		| 14 |
| 15 |		| 16 |
------		------

RAID 1 - Mirror:
======================
Disk 1		Disk 2
------		------
|  1 |		|  1 |
|  2 |		|  2 |
|  3 |		|  3 |
|  4 |		|  4 |
|  5 |		|  5 |
|  6 |		|  6 |
|  7 |		|  7 |
|  8 |		|  8 |
------		------

RAID 3 (unusual):
======================
P = Parity information

Disk 1	Disk 2	Disk 3
------	------	------
|  1 |	|  2 |	|  P |
|  3 |	|  4 |	|  P |
|  5 |	|  6 |	|  P |
|  7 |	|  8 |	|  P |
|  9 |	| 10 |	|  P |
| 11 |	| 12 |	|  P |
| 13 |	| 14 |	|  P |
| 15 |	| 16 |	|  P |
------	------	------

RAID 5:
======================
P = Parity information

Disk 1	Disk 2	Disk 3
------	------	------
|  P |	|  1 |	|  2 |
|  3 |	|  P |	|  4 |
|  5 |	|  6 |	|  P |
|  P |	|  7 |	|  8 |
|  9 |	|  P |	| 10 |
| 11 |	| 12 |	|  P |
|  P |	| 13 |	| 14 |
| 15 |	|  P |	| 16 |
------	------	------

RAID 0: Striping. Two disks where the data is spread across the disks so that every second block is on one of the disks.
+ Improves speed.
- Unsafe.

RAID 1: Mirroring. Both disks contain the same data.
+ Safe.
- Wastes half the space.

RAID 3: A third drive stored parity information (XOR). If one disk dies, the data can be rebuilt using this information. One disk is the parity disk. Can be used for more than 3 disks as well.
+ Safe.
- Requires complicated controller.

RAID 5: Every n:th block in an array of n disks is a parity block. If one disk dies data can be saved. Can be used for more than 3 drives.
+ Safe.
- Requires complicated controller.

RAID configurations can sometimes be combined if the controller alows it. For example, RAID 50, RAID 10 and so on. RAID 50 requires at least 6 drives.

All RAID configurations require the disks to be of the same size. If they are not the size of the array is based on the size of the smallest drive.

If you don't have drives with the same size and want to run them as JBOD (Just a Bunch Of Disks). A bit like RAID 0 except it's not faster than a single drive.