New to raid

[DarkManX4lf]

I have a Asus m3a78t 790gx/sb750. I want to build a raid setup with 3 Seagate 7200.12 1tb drives. What is the max amout of drives the sb750 chipset can handle in a raid 5 setup?

If I wanted to add another 1tb drive to the raid 5 setup without loosing data, is the possible on the sb750 ?

 

[Emulex]

consumer drives will fall apart in a cheaper raid setup.

just asking for trouble and write performance will be so sad its not funny.

trying to save you some misery when it all blows up. been there - done that - several times - even had oems ship out sata raid with consumer drives - guess what they failed too; days or weeks.

i ended up using my consumer drives as jbod . they work quite well in that role. they failed about every week with matrix raid due to not having TLER-like behavior.

 

[lopri]

Originally posted by: DarkManX4lf
If I wanted to add another 1tb drive to the raid 5 setup without loosing data, is the possible on the sb750 ?

Possible, but not a good idea. Mobo based RAID5 isn't reliable nor performant enough to warrant the hassle, IMO. Besides that you will run into MBR limit (2TB) which may complicate the matter if something goes wrong. Totally defeats the purpose of RAID.

 

[pugh]

What they said. Go Hardware RAID or leave that software junk alone. You will be much happier.

 

[DarkManX4lf]

Originally posted by: lopri

Originally posted by: DarkManX4lf
If I wanted to add another 1tb drive to the raid 5 setup without loosing data, is the possible on the sb750 ?

Possible, but not a good idea. Mobo based RAID5 isn't reliable nor performant enough to warrant the hassle, IMO. Besides that you will run into MBR limit (2TB) which may complicate the matter if something goes wrong. Totally defeats the purpose of RAID.

So there is a 2TB limit? So if I RAID5 3 x 1.5TB drives I wont see more than 2TB ?

 

[pjkenned]

What you do, if you have a larger than 2TB array, and need to use MBR (not really an issue with Win 7 which is what people will be running soon), just create a 2TB MBR volume, then with whatever you have left do either more MBR <= 2TB volumes or a big GPT partition.

Then again, 3x 1.5TB drives = 3TB usable so you would have a <=2TB MBR volume with the remainder to play with.

 

[Lucky Stripes 99]

I can attest that software RAID5 is fairly sluggish when it comes to writes. This is even with an Athlon X2 4850e (2.5GHz×2) and a trio of 640GB Caviar Blue drives. Whatever you do, don't put your pagefile on a software RAID5 drive.

As for the failures that the people above mentioned, I never ran into them. I used RAID5 with those Caviar Blue drives for almost a year w/o issue. That said, I had a pair of 80mm fans blowing directly on my drive cage.

If you're not going to use the array as your boot drive, you can also utilize Microsoft's built-in software RAID5 system. It comes standard with Server and Datacenter editions of XP/Vista/7.0, although you can google an easy hack to enable it using Workstation and Home editions. It does involve converting your drives from "basic" to "advanced" in the NT drive manager, which breaks compatibility with Linux, AFAIK. However, it might get you around the 2TB limit.

 

[Madwand1]

Originally posted by: DarkManX4lf
I have a Asus m3a78t 790gx/sb750. I want to build a raid setup with 3 Seagate 7200.12 1tb drives. What is the max amout of drives the sb750 chipset can handle in a raid 5 setup?

If I wanted to add another 1tb drive to the raid 5 setup without loosing data, is the possible on the sb750 ?

1. AMD SB750 can handle 6 drives in RAID 5.

2. Yes, SB750 has a "migration" feature which can non-destructively add drives to an array.

The 2 TiB limit is gone with OSs after but not including XP-32, including XP-64, 2003, Vista and W7, via GPT.

SB750 has "unoptimized" RAID 5 write performance, which is roughly proportional to 1/2 a single drive's write speed for sequential writing, whereas an optimized implementation can get around (n-1) x single drive write speed where n is the total number of drives in the RAID 5 array.

In practice this means that SB750 writes will be somewhat sluggish, comparable to USB drives or ordinary SD cards for sequential writes, varying according to the speed of the drives and their crowding. As usual with HDs, performance will steadily decrease as the drive gets full -- data stored toward the end of the drive will be proportionately slower to write or access.

Slow RAID 5 write speed has less impact when writing to the drives across a network. In these cases, the network is part of the bottleneck. In the case of a wireless or 10/100 Mb/s network, the network alone is the bottleneck, so the RAID 5 write performance hit can't be seen, but you shouldn't be using such a network these days for file accesses, esp. when you're hitting TiB sizes.

Vista and later mitigate some of this by expanding the size of the write requests. RAID 5 also has no negative impact on sequential read speed, which increases that proportionately to the number of drives.

Too bad AMD hasn't yet implemented a write-back cache as Intel has -- this would have solved the RAID 5 write performance issue.

 

[Nothinman]

I can attest that software RAID5 is fairly sluggish when it comes to writes. This is even with an Athlon X2 4850e (2.5GHz×2) and a trio of 640GB Caviar Blue drives. Whatever you do, don't put your pagefile on a software RAID5 drive.

If you're talking about that onboard, crap RAID then, yes I wouldn't trust it with anything. Good software RAID 5, like in Linux, beats most hardware RAID. I don't think any piece of hardware will be be slowed down by a driver than can do XOR calculations at 8GB/s via SSE with my host CPU.

It does involve converting your drives from "basic" to "advanced" in the NT drive manager, which breaks compatibility with Linux, AFAIK. However, it might get you around the 2TB limit.

Linux can read dynamic disks and GPT partition tables, however I would avoid dynamic disks.

The 2 TiB limit is gone with OSs after but not including XP-32, including XP-64, 2003, Vista and W7, via GPT.

Except that you still need a legacy BIOS partition table for your boot drive unless you've got a motherboard running EFI.

 

[Madwand1]

Originally posted by: Nothinman
Except that you still need a legacy BIOS partition table for your boot drive unless you've got a motherboard running EFI.

Yes. I presumed however that the OS and data storage were separate, as I think they should be for easier maintenance, portability, etc.. This is an issue to consider though, as you might need an IDE drive, IDE-SATA adapter, or some other solution to add another port, as well as the additional drive.

 

[Nothinman]

Originally posted by: Madwand1

Originally posted by: Nothinman
Except that you still need a legacy BIOS partition table for your boot drive unless you've got a motherboard running EFI.

Yes. I presumed however that the OS and data storage were separate, as I think they should be for easier maintenance, portability, etc.. This is an issue to consider though, as you might need an IDE drive, IDE-SATA adapter, or some other solution to add another port, as well as the additional drive.

Yea, a separate OS drive is always the better idea but there's a lot of people that don't think about that.