RAID confusion

[Impaler]

In light of recently having my 8 month old 80GB drive die I have decided to build a new pc using RAID 1. I plan to (unless I find a reason to do otherwise) buy either a Abit NF7-S or Albatron KX18D Pro II and 2 Maxtor 120 gig 7200rpm SATA drives for this. Now my personal experience with RAID is non-existent at this point so I was hoping that I could have a few questions cleared up...

1. Firstly as I understand it the system recognizes the array as 1 drive but does the RAID controller algorithm place any limitation on how I can partition the drive etc?

2. I have read that most on-board RAID controllers use the PCI bus and take a significant performance hit over native RAID controllers. How do I tell if the RAID controllers on the mentioned boards are native or not?

3. Will the overhead with the pagefile be significant ? Obviously I am not worried about loosing that data and it makes sense to me that a bit of performance could be lost here. I was considering placing an other drive (may not be as fast) in the system to run the pagefile if this would be worthwhile.

4. On a post on this forum I read that it can be difficult to move the array to another computer with another controller. How Difficult? I?m not keen to have my redundancy/data lost simply because the mobo/RAID controller packs it in. I will definitely be doing this in the future for upgrades too.

5. On installation will the motherboard have separate SATA connectors for the RAID controller or is there jumpers / bios settings I change and use the 2 normal ports on the board?

6. Also as far as drivers are concerned will I need them? The RAID is integrated so will there be bios settings for this? If not will I simply need to boot from a disk and install some drivers supplied with the mobo?


I purposely haven?t given specs as this pc doesn?t exist yet but if I left something important out just ask. Thanks to anyone who can answer some or all of these questions.

 

[Hoffcorp]

I hear a lot of people talking about RAID performance and what is slightly faster than something else. How fast do you want your computer to be, if the conventional memory read and write speed isn't the critical part of the equation slowing everything down or you don't need super speed I would suggest taking into account cheaper boards because buying something you don't use is a bad deal. A lot of people always suggest the bigger and better gadget but often that is only appreciated once, when running a performance benchmark program and is hardly noticed in daily operation. Most the motherboards I have seen with RAID controllers don't require that you change any jumper settings, you select raid controller options in the setup during bootup.

 

[BG4533]

1. Shouldnt. You can have 1 big partition or 10 if you want.

2. I believe only some new intel boards and maybe the nForce3 have native SATA. I wouldn't worry about this all that much, but it is a nice addition.

3. If you have enough RAM don't really worry about the pagefile. Don't know otherwise, not sure what you mean by overhead.

4. Maybe impossible. Different controllers work differently. You should be able to switch between mobos/controllers that use the same RAID controller, but I dont think you will be able to use a different brand/model controller.

5. On my board and most I have seen the RAID controller has its own BIOS that detects the drives. You can set options in the BIOS for RAID. If you don't the drives are acted upon individually.

6. Yes there are drivers. You will probably have to supply them to your OS upon installation if you want to boot from your RAID.

Goodluck,
Brian

 

[Impaler]

@Hoffcorp's reply
I'm doing RAID 1 therefore the performance will be less than that of a single drive. So I'm obviously not doing it for the performance. That said I still want to get as much out of my system as I can. I also am leaning towards the Albatron board for reasons other than the RAID support.

@BG4533's reply
I do not like the idea of not being able to move the array. At all. This defeats the purpose of doing this if my data can still become unrecoverable. I assumed that the controller simply wrote the data to both discs when in mode 1. Therefore I don?t see why I wouldn't be able to run one of the drives independently if I wanted to (though I can see issues putting it back in the array). Is the data stored differently? I can see issues when operating in other RAID modes (0,5,etc) due to differing algorithms of the controller but how does this apply to mode 1? If the controllers do need be the "same" however does same mean same make/company or specific model/revision?

Thanks to you both for your input.

 

[Hoffcorp]

I have dealt with RAID controllers that use RAID1 but not all RAID1 are the same, some systems do it differently and that is just part of life, some systems write different files to the hard drive etc to help them run the system. It is always possible to recover the information but it can take some work on your part, the information is there to be recovered whether or not it works with the default settings on your other machine. Usually RAID1 is used incase one drive fails, the motherboard failing is a different ballgame because its not designed to be used for that type of redudancy.

 

[Impaler]

OK that makes enough sense to me, taken the data will not be identical. But you say here that recovering the data may take some work. Work I don't mind it was the impossible part that I didn't like. Motherboard failure or upgrading will have the same effect as I see it, the array will be required to run with a different controller. This will happen eventually. The data is still there I couldn?t see how it could be lost. If I have to muck about for a bit to get the array on another pc so be it. I do not plan on doing this very often.

 

[BG4533]

The following are my ideas, not fact:
I think specific RAID chipsets should be compatible. Different revisions would likely be compatible as long as there werent major changes made. The only reasons major changes are usually made are due to problems which you would have probably experienced anyway.

With that said, if you get a mobo that has an onboard SI3112 chip and run RAID you likely can run the array on a different mobo with an SI3112 chip. I also imagine you can run it on PCI based SI3112 controllers.

If you are really worried about a mobo failure or upgrade often consider getting a PCI based controller. You will be able to move this between mobos in case of problems or upgrades. These should also be cheaper and easier to replace if there are problems. Most of them start at around $35. I just bought one for $21, but I couldnt find anything on it online. We will see how it does.

Brian

 

[Impaler]

Hmm well I can't say I upgrade particularly often I'm pretty much going from a celeron 433. The point of the matter is eventually I will want to move these drives. I will price up PCI RAID cards tomorrow and also look at what types of RAID controllers seem to be popular for putting on-board. I think I will most likely just go for the on-board solution when it needs to be changed I?m sure I'll eventually get it working.

Also I hail from Australia so while I appreciate you looking online it will be of little use to me.

 

[Impaler]

OK I have decided to go with the onboard solution ala the Albatron board. In the end I realized that when I eventually upgrade I will probably be better off with a native RAID solution anyway so I lost my enthusiasm for a PCI card. PCI cards aren?t particularly all that cheap or easy to find down here in OZ either.

Thanks for the help guys I?m going to go turn this system from concept to computer sometime next week.

 

[sunase]

You might want to consider software raid. 2k/XP you can mirror the boot drive no problem and then you can run fine on just one disk when one fails and can even use the machine while it regenerates the replacement. I haven't tried hardware raid mirroring, but I *suspect* you would be stuck sitting in a bios menu while it regenerates (especially with the cheap sort of hardware raid that gets integrated into motherboards).

I've transfered spanned and striped software raid sets between windows computers without any problem (you just import them from the disk manager, no hardware other than normal ide/scsi/etc needed) and in fact I started using software raid after a pci raid card died on me and I had to buy a new one to get my data (and this was an expensive raid card with a significant processor and a large cache). All those niceties at the cost of a little performance - and with only two drives software raid is even closer to hardware (from my dim recollections of a comparison arstechnica did).

 

[wetcat007]

Originally posted by: Impaler
Hmm well I can't say I upgrade particularly often I'm pretty much going from a celeron 433. The point of the matter is eventually I will want to move these drives. I will price up PCI RAID cards tomorrow and also look at what types of RAID controllers seem to be popular for putting on-board. I think I will most likely just go for the on-board solution when it needs to be changed I?m sure I'll eventually get it working.

Also I hail from Australia so while I appreciate you looking online it will be of little use to me.

Wow... you use a 433MHz Celery?

 

[Impaler]

@ sunace's reply
I will be wanting to have a dual boot between xp, 98SE and am also keen to install a linux distro and become a bit more familiar with that. So the RAID needs to be a lower level and I don?t think this is an option and is why I didn?t consider it.

@ wetcat007's reply
Yep up till 7-8 months ago I was on a celeron 433. It got upgraded when the motherboard died after 3 and a bit years. Basically funds were low as college payment was due and a crap mobo and xp1600 were in order. So now a decent upgrade comes. Playing UT2003 in a decent detail is going to be sweeeeet.

 

[CryHavoc]

remember that in a raid 1 configuration, you must use two same size drives, and that the data will be duplicated across both drives. Not different data on each drive. With raid 1, if you loose one drive, the other mirrored unit will have the complete data on it. If you use Serial ATA, you can hot swap another drive in place and reset your raid, so that the data will be remirrored onto the new drive.

I mainly know Novell's usage of Raid. At work, we use raid 1 almost exclusively with each drive(s) running off an independant controller, but we have been moving to dedicated raid controllers and moving to at least raid 3, utilizing a hot spare.

nullHere is the Anandtech article explaining raid in detail.

 

[Impaler]

Hmm that link doesn?t quite work. But yeah it was the first article I read. I thought it was good.

I will be buying 2 drives from scratch exactly the same as I stated in my first post. Do you know however if it is possible to initially add data to one drive and then put both drives into the array and have the card create the array and then mirror the data to the second drive? This would make installation easier for me if it is possible.

 

[Sideswipe001]

Originally posted by: Impaler
Hmm that link doesn?t quite work. But yeah it was the first article I read. I thought it was good.

I will be buying 2 drives from scratch exactly the same as I stated in my first post. Do you know however if it is possible to initially add data to one drive and then put both drives into the array and have the card create the array and then mirror the data to the second drive? This would make installation easier for me if it is possible.

As far as I understand it, you will need to install both disks and form the RAID array before you can put data on a disk. At that point, it will duplicate everything that you do to one. I don't think it should be a very noticeable hit in performace. You'd take more of a hit using the software based RAID that someone mentioned in 2000/XP.

As a note, from my experience, RAID arrays generally only work with the controller type that made them - chipset - although, I have been able to move from one Promise controller to another without losing my Array before. I could not, however, go from a Promise to an Intel RAID controller.

Oh, as for the drivers - some RAID controllers double as ATA133 controllers. If that is the case, you'll have to go into the BIOS and make sure it's set to run in RAID mode. You will then NEED drivers to feed the 2000/XP install. It will ask you to press F6 right when the install starts, and then come up after a few moments prompting for a disk with the drivers. You must have a disk - not a CD. So make sure you throw the RAID drivers (again - if it's a UDMA/RAID controller, make sure you get the RAID ones and NOT the UDMA ones) onto a disk, and you should be all good to go.

 

[Impaler]

Originally posted by: Sideswipe001
As far as I understand it, you will need to install both disks and form the RAID array before you can put data on a disk. At that point, it will duplicate everything that you do to one.

That?s what I thought too. I was hoping there was a way around it but nevermind. I will plug in another drive and transfer data from that.

As for not being able to use a cd for drivers is this only when installing windows from cd? I will put the setup onto the drive first and install from there. Anyway if this doesn?t work I'll then put the drivers on a disk and do as you say.

After writing this I can see myself wanting some dos RAID drivers to get me up and running. Are my chances good of getting these with the mobo and if not are there ones available online?

 

[BG4533]

Originally posted by: sunase
You might want to consider software raid. 2k/XP you can mirror the boot drive no problem and then you can run fine on just one disk when one fails and can even use the machine while it regenerates the replacement. I haven't tried hardware raid mirroring, but I *suspect* you would be stuck sitting in a bios menu while it regenerates (especially with the cheap sort of hardware raid that gets integrated into motherboards).

I've transfered spanned and striped software raid sets between windows computers without any problem (you just import them from the disk manager, no hardware other than normal ide/scsi/etc needed) and in fact I started using software raid after a pci raid card died on me and I had to buy a new one to get my data (and this was an expensive raid card with a significant processor and a large cache). All those niceties at the cost of a little performance - and with only two drives software raid is even closer to hardware (from my dim recollections of a comparison arstechnica did).

All RAID on consumer motherboards is software RAID. There is hardware involved, but all it does is act as a controller and make the array bootable. The CPU does all of the RAID calculations necessary. Real hardware RAID has an onboard processor so the CPU has to do little to no work. The difference between software and hardware RAID is usually pretty negligible for desktop machines.