4 drive Raid 1 array on ICH9R

There is no logical reason to have more than 2 disks in a RAID 1 array, unless you are just over paranoid and feel you need to have 4 identical copies of your boot drive running all the time.
There are far, far, better ways to back up data.
I think maybe you are lacking somewhat in the understanding of what RAID is, what it does, and what the different types of arrays are for.
Maybe you are thinking of RAID0+1, which is two mirrored sets of drives running in RAID0?.

Well, I must say, that is a new one...no such thing as full hardware RAID 11 other than with some dual controller set-ups ( hp/compaq servers come to mind ). This will not work for an OS drive however, you can software RAID 1 2 hardware RAID 1 volumes. I've never heard of anyone doing it with RAID 1, but it is common on large scale arrays running RAID 5 ( RAID 51 ) to guard against individual controller failure. You are kinda screwed with the RAID 0+1, I agree. You could however, use this same technique to create a true RAID 10 volume ( assuming its not the OS drive ) by software striping the 2 hardware RAID 1's. While I don't exactly trust windows to handle rebuilds in the case of failures, it is definately do-able. RAID 10 will provide more fault tolerance than a RAID 5. You could handle 2 simultaneous drive failures as long as they're on seperate RAID 1 arrays and the windows software RAID 0 wouldn't even notice.

If you need to boot from one of these 4 drives, then your best bet is 2 sets of RAID 1. At least you're not putting all your eggs in 1 basket.

Kudos to you for understanding the rebuilding performance penalty, most do not.

@croc

I've read this and many more docs on the Intel site before posting and you should do the same and also read with more attention the posts
before you answer to them to avoid out of topic messages like your last one: Intel® Matrix Storage Manager allows 2 raid sets on the same
disk set.

@ ShadowFlash

Thank's, maybe I'll try two 2 Disk RAID 1 sets and backup the relevant data from one to the other during non-business time,
this would improve redundancy vs. RAID 10.

@croc

As you said maybe I don't comprehend what i'm reading, that is the reason why I'm posting on the forum: to get some hints by some lovely person ( e.g like you), nonetheless:

1) I don't want to buy a raid controller
2) I don't want to run a Matrix raid combination
3) I don't want to be spoon fed
4) I don't want to get on your nerves

There is a simple solution to avoid it just don't answer to threads of people that "get on your nerves"

5) I wonder if with the ICH9R it is possible like with other Software raid implementations (Linux raid) to run 4 disk raid 1 arrays

If you have a better understanding of the docs a simple yes or no would suffice.

6) I'm asking if somebody tried this already so that I know it surely before buying 4 rather than 2 disks.

Ciao

I myself run a 4 disk RAID 1 but it is implemented with linux software RAID

Personalities : [raid1] [raid6] [raid5] [raid4]
md2 : active raid1 sda1[0] sdb1[1]
244195904 blocks [2/2] [UU]
bitmap: 0/233 pages [0KB], 512KB chunk

md0 : active raid1 sdc1[0] sde1[3] sdf1[2] sdd1[1]
104320 blocks [4/4] [UUUU]
bitmap: 0/13 pages [0KB], 4KB chunk

md1 : active raid5 sdc3[0] sdd3[3](S) sde3[2] sdf3[1]
472535680 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
bitmap: 1/226 pages [4KB], 512KB chunk

Usually this is done in linux to place the boot partition on it so that you can boot your system indipendently of what drive failed if you have installed the boot loader on the MBR of each drive.

I did have a hot spare and used it to replace the first failed drive but another drive failed during the rebuild of the RAID 5 array. :_(
That's why i want to move to RAID 1.

Ciao

this is our raid device: md0
it is : active
in raid1 mode
composed by sata disk sdc partition 1 which is drive number [0] of the array
composed by sata disk sde partition 1 which is drive number [3] of the array
composed by sata disk sdf partition 1 which is drive number [2] of the array
composed by sata disk sdd partition 1 which is drive number [1] of the array
the raid device counts 104320 blocks
there 4 drives out of 4 expected drives [4/4]
all of them are Up [UUUU]

;-)

I set it up that way so i do know :-), however when i first experimented with it just to be sure i pulled out all the disks and having installed the boot loader on every disk the system booted the same from each of them.

In my actual box i used 4 disks as it is a multiple raid array on the same disk set and the number was due to the raid 5 set composed by 3 disks plus 1 spare drive.

| |DISK1|DISK2|DISK3 |DISK4|
---------------------------------------------------------------------------------------------------------------
| Partition 1|RAID1|RAID1|RAID1|RAID1 | (contains the kernel and an initial ramdisk to boot the system)
| Partition 2|RAID5|RAID5|RAID5|RAID5 SPARE| (contains the root file system)
| Partition 3| SWAP|SWAP|SWAP |SWAP | (non Raid, as Linux Kernel does some striping out of the box if multiple swap devices are present and set to the same priority)


Would like to do something similar on the ICH9R with winxp so that all but 1 disks of the set can fail and i still would be able to run the system during business time and replace the failed disks during non business time.

Ciao

Intel's software RAID stack only supports RAID 1 with two disks.

The disk limits for the various RAID levels are as follows (some ssytems may be more restrictive):

RAID 0: 2-6 disks
RAID 1: 2 disks
RAID 5: 3-6 disks
RAID 10: 4 disks
Intel Rapid Recover Volume: 2 disks