Noobish RAID question

knowledge123 · 26 Mar 2008 at 08:45

hey all,

I'm thinking about setting up a RAID config (more likely RAID 1) for my rig, and I have a simple question, I have google and searched but I can't find a definitive answer.

I already have my Vista 32 HP setup exactly how I want it on my current HDD, and my question is; on setting up the RAID, do I have to format the currently installed HDD, or is it possible just to plonk the 2nd HDD in and for it to copy the data across on installation of RAID ?

thanks

rpstewart · 26 Mar 2008 at 09:04

It depends....

1) Normally the SATA drivers used for RAID mode are different from those for single drive operation. Unless you have a second SATA controller onboard it's difficult to change the drivers over because the RAID drivers cannot be loaded unless the SATA ports are set to RAID mode in the BIOS and the system cannot boot in that configuration with the single drive mode drivers.

2) Not all SATA/RAID controllers support migration from single drive to RAID1 once the driver issue is sorted. NForce ones do but I'm not sure about Intel. You should, however, be able to use Acronis True Image to take an image of the single drive and restore it to a new RAID1 array assuming you get all the driver issues sorted.

Finally you do realise that RAID1 will mean a performance hit over a single drive. None of the motherboard based RAID solutions support split reads and write performance will take a hit because the controller ensures both disks are finished and verifies the writes before telling the OS that the operation is complete.

knowledge123 · 26 Mar 2008 at 09:22

Hmm, intriguing, never simple, is it ?

Thanks for that. I have an Asus P5B Deluxe motherboard. So point 2 you made would definitely cause me concern.
i could go for RAID 0, I suppose, if that didn't make read/write slower, but having the redundancy failure protection is a big tick for me.

fobose · 26 Mar 2008 at 09:29

rpstewart: does something like the Adaptec AAR-1430SA support split read and writes?

rpstewart · 26 Mar 2008 at 10:20

It's difficult to tell since most manufacturers don't advertise whether they support split reads or not. 3Ware are the only folk who seem to make a song and dance about it, they have a semi intelligent system that uses split reads for some long sequential reads but not for random reads.

Bito · 26 Mar 2008 at 23:34

You can attach the current drive to the Jmicron e-SATA controller port on the P5B Deluxe.
Then change the bios setting to RAID for the Intel controller.
This will allow you to boot up on the Jmicron controller, in ide mode, then install the Intel RAID drivers for the Intel controller onto the drive when you next boot into Vista...have the drivers ready

Afterwards, simply put the drive back to the Intel port whilst leaving the setting on RAID.

Intall the Intel Matrix software, add 2nd drive and the Intel Matrix software will ask what you want to do with the new drive.....RAID 0 or RAID 1

Job done.

Snapshot · 27 Mar 2008 at 06:09

I would follow Bito's suggestion. I always use RAID1 where possible and any performance hit is negligible with modern drives.

knowledge123 · 27 Mar 2008 at 06:40

Nice! Many Thanks Bito, and all those that replied

Top stuff

NathanE · 9 Apr 2008 at 18:55

rpstewart said:
Finally you do realise that RAID1 will mean a performance hit over a single drive. None of the motherboard based RAID solutions support split reads and write performance will take a hit because the controller ensures both disks are finished and verifies the writes before telling the OS that the operation is complete.

You have no idea how much bother this has caused me with one of my friends. He took your comment here as gospel and started saying one of his reasons for getting a RAID 1 array was false (which I had told him).

Well I can hereby tell you that you are completely and utterly wrong on this point.

http://download.intel.com/design/chipsets/applnots/31085501.pdf

Please see Page 10.

It explicitly states that Read Performance *is* improved with better concurrency. And that it uses an algorithm to effectively distribute read requests between all hard drives in the RAID 1 array. The algorithm takes into account two factors; disk head positions and disk read queue length.

Sheesh.

PS: Yes I have little doubt that some crappy "JMicron" or whatever RAID controller won't have this simple and basic optimisation that takes about 5 minutes for any programmer to write.

PPS: Looking at your posting history you have posted this misinformation in almost countless threads. Might be worth contacting them because people may be running sub-optimal hard drive configurations as a result.

rpstewart said:
It's difficult to tell since most manufacturers don't advertise whether they support split reads or not. 3Ware are the only folk who seem to make a song and dance about it, they have a semi intelligent system that uses split reads for some long sequential reads but not for random reads.

Why would 3Ware make their algorithm not load balance random reads? That would reduce performance. Random reads benefit most in fact! Sequential reads, provided they aren't interrupted, should be kept on the same disk for as long as possible. Otherwise the disk's cache and sequential read optimisations aren't going to be used effectively.

rpstewart · 9 Apr 2008 at 21:23

Woah, calm down.

So I got something wrong based on personal experience and the available information, it's hardly the end of the world.