Three 2TB HDD + ICH9R + RAID5 = FAIL. Why?

[lkjhgf]

Hi, I just built a raid5 with three 2TB harddrives, but Windows (XP pro 32 bit) doesn't see it at all. That's strange because I've initialized the raid too and in the intel matrix storage console looks everything ok but it's not. It's 150 GB RAID0 (and windows can see it as I can use it) + a 3600GB RAID5 (and I can't see it nor use it) HDTune sees a strange HDD of 2199 GB and it gave me ~80000 MB/s as a read benchmark O_O (the fact is, that I don't have a 2199 gb nor partitions...) I Already have the ~same configuration on the same southbridge with three 1TB harddives and everything is ok... What's the problem? :-/

 

[Emulex]

2TB is limit man for that type of partition. split it 1800/1800 and you will be good to go.

or gpt and use a mount point. not sure if XP supports that but 2008/7/vista have no problems.

 

[RebateMonger]

XP x32 doesn't support GPT at all. As Emulex notes, you can split the 3.6 TB array into two 1800 GB virtual disks and should be able to partition those virtual disks under XP using MBR partitions.

 

[lkjhgf]

Damn. After I posted I tried to play a little bit with those RAIDs and I've created a 1,64 and a 1,99 TB RAID5, it worked but I get slow speeds... If I upgrade to 7 can I create a simple 3,6 TB RAID5 without further problems? (I mean: I install 7 then it will directly see my 3,6 TB?) Thanks for your answers

 

[Mark R]

The ICH9 RAID5 is unusably slow at the best of times.

Using a different OS won't improve it's desperately bad performance. Using software RAID almost certainly will, but that's a Pro/ultimate windows version only option.

 

[RebateMonger]

If I upgrade to 7 can I create a simple 3,6 TB RAID5 without further problems? (I mean: I install 7 then it will directly see my 3,6 TB?)

With Win7, you'll be able to create GPT partitions and use them as data (not boot) partitions larger than 2 TB.

Be sure you know how you are going to back up and perform other disk operations with the GPT partitions. Not all current disk and backup utilities know how to handle them.

 

[FishAk]

Make sure you have good backups, because you will eventually loose everything on your RAID 5 array. RAID 5 is a known troublemaker. For performance and reliability, RAID 10 is much better.

 

[Emulex]

no using a unstable software based windows raid with consumer raid drives is unstable.


i've noticed the newest boxes (DROBO,QNAP) now recode their drivers to ignore SMART/TLER/CER/whatever and just roll on their own schedule.

I got this answer when my cam sent me a prettied up QNAP with AV drives (tler = 0 seconds, no error correction). That is the only way to reliably handle the mix of consumer and non consumer drives imo. smart move.

raid-5 is some sort of trophy status thing. it is not usable in a uncontrolled environment.

To me anything raid should never:
1. crash/reboot
2. lose power

ever. otherwise it should not have raid. this scenario does not happen in a controlled environment (think dual APC's with separate 110 legs with APCUPSD to shutdown).

You don't game/etc on systems with storage. they are storage servers.

I preach intel matrix raid is good only for raid-0 - i've been bitten hard by it several times. shame on me

 

[sub.mesa]

The ICH9 RAID5 is unusably slow at the best of times.

It is just as slow as any other RAID5 engine without write-back. The slowness comes from your HDDs as without write-back they would need to seek alot.

To write 4 kilobytes on RAID5 consisting of 8 drives with 128KiB stripesize, one would:
- read part of the existing full stripe block ( (8-1) * 128KiB = 896KiB)
- calculate new parity
- write new parity and block (at least 128K + 4K)

As you no doubt can imagine, this will be slow on any RAID5 engine.

However, you can get decent sequential write speeds with Intel RAID5 if you enable the 'Write Caching' option in Intel's RAID drivers. This will enable RAM write-back buffercache. Warning: this could kill your entire filesystem in case of crash (BSOD) or power failure. Only use for fully backed up system disks!

 

[lopri]

To me anything raid should never:
1. crash/reboot
2. lose power

ever. otherwise it should not have raid. this scenario does not happen in a controlled environment (think dual APC's with separate 110 legs with APCUPSD to shutdown).

You don't game/etc on systems with storage. they are storage servers.

I preach intel matrix raid is good only for raid-0 - i've been bitten hard by it several times. shame on me

I agree.