RAID Help

DJohnsonRose

Can someone explain to me what RAID 2,3 & 4 are please? I have tried using CBT nuggets and online materials but i can't seem to get my head round it? Also can someone explain to me the difference between RAID 10 & RAID 1+0/0+1, I have looked on iSCSI RAID Switch, External SATA RAID, vmWare Storage-NAS Network and SAN Data Storage Solutions with JetStor but it looks the same asides from the blocks being copied in a different order. What difference does it offer when you measure the I/O or throughput?Any help would be greatly appreciated as I am taking this exam next week!Thanks in advance guys

jibbajabba

Raid 1+0 / 0+1 is explained a bit better here.

Raid 2 / 3 / 4 is a explained a bit better here and here.

Main difference in certain Raid levels is how data is striped - it can be BLOCK based or BIT based ... easy to miss (the difference that is), which might make it confusing at first.

I have never taken this exam, but I am working in IT for 15 years now and I never came across a Raid 2, 3 or 4 impolementation

Edit: forgot I DID take Server+ as an early beta .... lol

DJohnsonRose

Thankyou! I understand RAID 01 & 10 now!!! RAID 2,3,4,6 are a bit more tricky, did you need to learn this for your server +?Do you know where I can take a practice test?

DJohnsonRose

So whats the difference between a bit and block? I am aware that 8 bits make a byte but where does a block come into this? Also what's the advantages/disadvantages of striping data at the block level and bit level??

EV42TMAN

granted i don't know how much the test is going to cover RAID but in the real world you'll be using 0,1,5,6,10 and maybe 50,60 if in a enterprise. if i remember correctly raid 5 pretty much made 2-4 useless.

dover

Here's some info I used while studying for the CISSP.

I typed all this info and then ran across this site - quick and dirty RAID info: Basic RAID Organizations

RAID-0 Striping
No redundancy
Stripes across all disks in an array using all available drive space
Maximizes space and improves read/write performance

RAID-1 Mirroring
Duplicates data from one disk (or set of disks) to another disk (or set)

RAID-2
**Requires 39 disks - 32 disks for data, 7 disks for error-recovery code
RAID 2 system would normally have as many data disks as the word size of the computer, typically 32
With 32 data disks, a RAID 2 system would require 7 additional disks for ECC
Data is interleaved at a bit level and can withstand losing 4 error-recovery drives without affecting data

RAID-3 and RAID-4
Data striped across a variable number of drivesHas a dedicated parity drivethat can be used to reconstruct data from any single crashed data driveRAID 3 utilizes byte level parityRAID 4 utilizes block level parity

RAID-5
Stripes data and parity calculations at the block level across all drives
Parity information is interleaved
Disk reads and writes are performed concurrently
No dedicated parity drive

RAID-6
Extends RAID 5 by adding a second parity block distributed across member disksYour array can lose two drives without data loss - protecting against data loss during a rebuild of a failed driveThere is a performance hit for write operations as two parity operations are written across the array

RAID-7
Identical to RAID 5 but array functions as a single virtual disk in hardware