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Hard Drive Configuration Question - RAID Mirror and LVM
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Author:  ik632 [ Wed May 18, 2005 11:56 am ]
Post subject:  Hard Drive Configuration Question - RAID Mirror and LVM
Hey guys, I've been testing Knoppmyth on my "spare" 60gb Maxtor for about 2 months now and I'm happy with how it's working. I am going to do a fresh install onto the real hard drives that I have. My question is that I have 2 Western Digital 80gb special edition 8mb cache and 2 Hitachi 200gb 8mb cache drives. I have a Soyo KT400 Dragon Ultra Platinum board with built in PATA RAID.

I've had issues with getting the RAID working properly (I can see the drives, but the two drives in the mirrored set are shown rather than the mirror volume and I can mount either of them, not just the mirror set). I want to use the raid and keep either the two 80's or the two 200's in a mirror for backup of other things I have.

My question is; Should I install on the 80 and LVM to include the other 80 while keeping the 200's in a mirror set, or should I install on the 200 and LVM the other 200 and keep the 80's in a mirror set?

My biggest problem is that the 200gb mirror is split into two partitions with one being just about full (90gb or so) and that is purely a backup that I don't access all that much. I want to have plenty of room for recorded shows but I also want my RAID mirror to be as large as possible with matching drives.

Right now I am leaning towards keeping the 200's in a mirror set and installing on the 80's and using those for video storage. I can have 8 IDE drives on that motherboard, so I was thinking I'd pick up another drive (there's a 300gb on sale at CompUSA for $149) and include that in the LVM. Do you guys and girls agree?
Author:  Girkers [ Wed May 18, 2005 4:33 pm ]
Post subject: 
I can not comment directly on your Mainboard, but I have an onboard RAID and found that no matter how hard I tried, it would not show as a single drive.

The reason for this is that the MB manufacturers cut corners by using "Lite" version of RAID chips thus most of the work is done in software, which KnoppMyth does not have.

My MB using a Promise chipset even says it is a "Lite" chipset and it too identifies the HDD as separate drives.

Sorry I can't help you, but I thought I would give you my take on the situation.
Author:  willem [ Thu May 19, 2005 12:19 am ]
Post subject: 
The main question is: do you need redundancy? If so RAID is something to consider. From your post you mention mirroring (offers redundancy) and LVM (flexible way to expand storage space). Do keep in mind that mirroring only helps to keep your system going when one drive fails. It is no substitute for regular backups! This is a mistake commonly made.
Should you need the redundancy then software RAID as offered by the Linux kernel is probably a safe bet. There is a lot of info on the net about this. The main advantage is that software RAID is hardware independent. You can replace a motherboard in the future and transfer the RAID array to it. With the "hardware" RAID controllers (the cheap ones actually do some kind of software RAID too) the RAID array only works on the controller of a specific vendor.
From what I understand in your post is that you want to create some RAID 1 mirrors and have a single drive that you want to "LVM" together. Even though this is technically possible Mr. Murphy would tell you that the failing drive in the future is the single drive... Personally I would install the root fs and /cache fs on a single drive (hda) and create one LVM volume for /myth and add all drives to this volume. I wouldn't use RAID 1 since it would only cost me space and my system is allowed some downtime. Make sure you keep the drives cooled and properly powered to limit the risk of failure. Besides that make backups of the things you really want to keep.
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