Raid Setup & Configurations

[WeaponX 0]

Hi, someone asks me if I can setup their computers to use RAID. I read up on this as much as I could since I have never personally done this before. I read the article here but am quite confused how it worked in the example given there. They had two 74GB hard drives and at the end they have one 70GB partition and one 34GB partition. How did they get that and is there any space left after those two partitions are allocated the space? From what I see, it's 35GB from each hard drive to make up that 70GB for the striping right? The other 34GB is just for "one" of the hard drives, which makes it 78GB total (70+78=148GB which is the two hard drives combined size). Am I thinking this out correctly? I always thought it required 4 hard drives if you want to do it this way. So now, with the setup they have here, is the whole machine set for striping and mirroring? Would there be a problem with the mirroring since the RAID1 volume (78GB) has a difference size than the RAID0 volume (708GB)?

Are there any major differences on how to setup RAID if they are using ATA/PATA or SATA? I see that the article mentioned installing the SCSI adapter drivers. If the computer has RAID support already, is this step necessary or can I just go on using it without the need for any additional drivers? The BIOS itself will have an option for RAID if they motherboard supports it right?

I'm not sure if he has Windows installed already, but if he does and he wants to go with striping, I assume this will mean I have to wipe out the drive and reinstall Windows once the RAID 1 is setup correct?

So many questions...just learning

Many thanks in advance.

[vujsa 0]

Well, I'm not going to read that particular article becasue I know what needs to be done and that article confused me pretty quickly.In most situations, you have two drive channels and each channel has a master and a slave drive for a total of 4 possible drives.To set up mirroring, RAID 1, you have to set up identical drives on the Master drive connector of each channel. They have to be on seperate channels.For the striping, RAID 0, the two drives need to be on the same channel. One as the master and one as the slave.If you want both striping and mirroring, RAID 1+0, then you will usually need 4 hard drives. All 4 drives should be identical but you can use 2 sets of 2 like so 40GB + 70GB on channel 1 and 40GB + 70GB on channel 2! It would show as a 110GB drive with a mirror!More than likely, the user will need to reinstall the OS if striping is desired since the data is stored on two drives. The RAID installer will format both drives for striping! All data will be lost on a drive that is formated in such a manner.Now it is possible with a four drive RAID 1+0 setup to set the striping up on one set then use them as the mirror for a single drive with the existing data on it. The move the striped setup to channel one as the active drive and install the other two drives in channel two. Then you can duplicate the active array onto the mirror array.Like so:[drive3] -> [drive1 & drive2][drive1& drive2] -> [drive3 & drive4]Where drive 3 is the existing drive with the OS etc...This is kind of a lot of work cause you physically have to swap cables and open and close the case several times with system startups inbetween!You can also to a 3 drive RAID 1+0 system where you may have two smaller drives and a larger one.For example:2 X 40GB HDD and 1 X 80GB HDD!if you strip the two 40's and have them mirror the 80, then it would work but your usable hard drive space would be about 70GB since each of the 40's will lose about 5GB in the process and the 80 cannot be larger than it's mirror.If the user only has two drives, then the best he can hope for is one or the other, not both. Some RAID software allows for some pretty tricky stuff where you can mirror a partition only or strip two partitions on seperate drives. This type of software RAID can be useful but varies with each program.Once the array(s) are set up and working, the user can do all of the normal drive operations including defrag, disk check, and partition and for the most part, the OS will never even know that there is an array set up. The only time it is ever an issue is if a drive fails!There are some pretty tricky installation issues with WinXP for some RAID controllers. I've aleays had to install the OS then swap all of the cables around and duplicate the drive to get it to work since WinXP would install directly to my RAID controller with the set up I prefered. But my controller was an add-on so it may be easier with a MB that is RAID ready!LEt us know what kind of set up the user wants and we can give you a better idea of what you'll need to do!vujsa

[WeaponX 0]

Thanks for the reply vujsa. I just got more information from the user. He said the motherboard supports RAID already, so hopefully that saves us an extra step. Will that require those SCSI drivers that I saw mentioned? Or does that only apply to actual SCSI adapters/controllers?He already has two hard drives on his computer. He wants me to setup up RAID with the two existing ones and add these two new 320GB SATA drives onto it. I asked him what the size are of the other two drives...still didn't get back to me yet.Is it possible to create a RAID setup where they are using different types of connections (IDE & SATA)?I like the RAID 1+0 setup that you mentioned there vujsa. I think that might be what I'm going to be leaning towards from what I see here. So if the user has Windows on the existing hard drive, I can "copy" the data from that drive into the two new 320GB drives as striping? If so, how about the second hard drive? He has another existing hard drive which I assume is for data storage only. What happens if the existing hard drives are smaller than 320GB? I know it won't be pretty...Let me know of any problems that I may run into when doing this as I don't think his two existing hard drives are at the full blown 320GB like these two new SATA ones are.EDIT: Just got more information from him. He wants his current two hard drives to be using mirroring for data backup. How would I go about doing this (put original on first channel as master and slave and the two 320GB SATA ones on secondary channel as master and slave?)? Also, what happens if they two current hard drives are smaller than 320GB? Will the rest of the extra space be wasted? What's the best way to handle this without wasting the space?Thanks.

Edited October 24, 2006 by WeaponX (see edit history)

[vujsa 0]

Well, I've never done this with SATA so I can't say what the controller is capable of. I'd really need to see the spec. for the MotherBoard to be sure of anything.You shouldn't need any SCSI drivers. WinXP may identify certain RAID drivers as SCSI but they will be IDE or SATA. As for combining the IDE and SATA, I don't know if it can be done! Really depends on the BIOS.If all 4 drives aren't 320GB which they probably are not, then I think that two seperate arrays would be best. As I understood you, he wants his two old drives in a RAID 1 configuration. One old drive as the active and the other drive as it's mirror. Is this correct?If so, I would set those up on IDE1 master and IDE2 master. I wouldn't put them on the same channel since it could really slow the system. The bus can write more quickly to two seperate channels than to the same one!I would then put the two new drives in a seprerate mirrored array. SATA1 master and SATA2 master.With that large of HDD's, I don't see that striping will really be useful. Most people use striping to artifically create a larger hard drive. Otherwise, you'll have to strip one old with one new and mirror it with the other old and the other new.If he has 2 X 80GB hard drives and buys 2 X 320GB hard drives and wanted RAID 1+0, this would be the configuration:[80GB & 320GB] as the active[80GB & 320GB] as the mirrordepending on the user interface for his RAID drivers, this could be very easy to do or nearly impossible if even allowed by the system.I'm sorry, I personally don't have any SATA drives and I'm a little out of practice with RAID setups. That and all of the unknown variables really makes it hard for me to be specific about what to do.vujsa

[WeaponX 0]

No problem vujsa. You cleared up a few points that I was confused about earlier by reading that article.The person hasn't asked me to take a look at his system yet, but if/when he does, I'll see what happens.What you said earlier makes more sense. According to how he said it, it sounds like he wanted to keep the two old drives and have the two new 320GB to be used as the main ones for mirroring and striping. This was where I was lost as it doesn't sound feasible as you said earlier (unless he actually does have two 320GB currently...which I also doubt).If he asks me to set this up for him, I will report back what happened...whether it's IDE and SATA or just plain IDE/SATA instead.Thanks again for all the help.