Configuration of an array will be entirely dependent on the hardware - You should go over your motherboard's documentation for that. I have not played with software RAID in Linux so I can't help you there, but I have read that it is fairly mature/stable. http://tldp.org/HOWTO/Software-RAID-HOWTO.html should get you started (again, no guarantees on how up-to-date it is...)

Hope you get it worked out...

K, I think I basically figured out that the VIA SATA chipset (VT8237R) is not supported by linux. O well. Can anyone recommend a 4-Port (For future expandability) PCI SATA raid controller card that is definitely supported by linux? I saw this one (Newegg) on newegg but I noticed something about requiring a floppy drive (which I don't have). I really just want something basic with plug and play that will get these damn drives working with the least amount of hassle.

I don't think Linux support would be necessary, as Linux doesn't have to know about the raid. I think you should do a test to see if it's working, and if it IS, then leave it alone.
Power down.
Unplug the power from one of the disks, or physically remove from the system.
Power up, and see if it works and if your data is present on hda
If so, power down, and switch to the other drive.
If you've got the same data on hda, then that should prove to you that the mirroring is (was) working properly, and that Linux doesn't have to know about it.

The only manufacturers I am aware of that have Linux supported real hardware SATA RAID controllers are 3Ware, Adaptec, and LSI Logic. I have not personally used them, I know of them through the network admins where I used to work. Check out the list here http://linuxmafia.com/faq/Hardware/sata.html but make sure to note real hardware RAID vs. "fakeraid".

As I recall, real hardware SATA RAID controllers that are supported in Linux are not inexpensive, something in the neighborhood of $150.00 US and up when I was looking (about 1.5 years ago).

I'll try this in a bit but the comp is in a really awkward spot, once it's in, it's a pain to get back out.


Yea, I'm not liking the $300 4-Port controllers.

Can I just mirror these with LVM? If this is correct (MythTV Wiki) then why wouldn't I just do this?

It is true that once the array is created, Linux won't know the difference between the array and a single disk. However, you will need drivers for whichever RAID controller you choose so yes, it would need to have Linux support.


Careful with this, if you break the array initialization you could lose data. Remember that it's the RAID controller that's working to keep the drives synced (in theory, this may not be the case in md10md's situation right now).

Yes, LVM would give you RAID capabilities, just make note of this under "Make the ARRAY":

Your data will be gone, so be sure to back it up!!

I don't recall, is this your boot drive? I'm not sure LVM on SATA boot drives is supported (seem to recall reading something like that awhile ago, not sure)

Yes, it is a boot drive, is there anyway to get around this?

Not that i am aware of (but I'm no expert and I've never used LVM to create a mirror), maybe someone else will have some better information on that.

Question: What are you trying to accomplish with the mirror? If it's to safeguard the data that's fine, but it doesn't replace a backup plan. If either of the drives were to die you would have a chance to replace it and keep your data, but if both drives go down, you're out of luck. I use an LVM for my media storage (videos, mp3s, pictures) and have another system with an LVM that I rsync to each night. Not a "backup" in the purest sense, but this way I don't have all my eggs in one basket, as it were. Gives me a chance to recover if there is a serious failure in either system.

That's right slowtolearn, I have a similiar setup using rsync. RAIDs do not safeguard against logical damage/corruption. Eg. You accidently do a rm in the wrong directory, it will be removed from both drives instantaneously. Whereas with a timed backup (simple rsync script, etc) you have a window to recover your losses (and also a window where it won't be completely backed up ).

Which is also why this solution is by no means the best If you don't catch the problem before the next rsync, then you have transferred the problem to the other system. Nothing beats a real backup scheme (full system and incremental, removeable media, etc.), but for most home setups a removeable media solution is much too pricey. This was the best I could come up with while keeping the price realistic.

The reason I wanted the raid was to safeguard against the loss of any files by disk failure. I want to have a place where I can just throw all my movies, music, and files and not worry that a hard drive crash will take everything down. I realize that if both drives go down I'm screwed but the probability that that happens at the same time is highly unlikely. I think what I'm going to do, and this seems perfectly possible, is reinstall KnoppMyth on an 80GB WD drive I have, delete the /myth folder, add the two 320GB SATA drives to a RAID 1 array with software, and set those to be the myth directory. Seems like that's the best option at this time.

That's your best bet at this point with one exception - You don't want to "delete the /myth folder". Mount your RAIDed 320Gb into /mnt, and copy the contents of /myth into /mnt. Then edit your /etc/fstab file to mount the RAIDed 320Gb into /myth. You retain the contents of /myth this way...

EDIT: Errm, looking at this again there is really no reason to throw 80Gb in there just for the OS. If you have anything smaller you probably want to use that (I have a 20Gb PATA drive for the boot drive, much more than I need as I have /myth on a 250Gb SATA drive). /EDIT

If you are just worried about the /myth directory (I sure wouldn't want to upload 200+ CDs again!), then you might want to reconsider the rsync option.

With raid, you will have both drives running all the time. Thats 2x the noise and 2x the wear and tear (okay, not quite since reads in theory should be shared).

I have my second drived unmounted and spun down with hdparm. Mythwelcome wakes my PC up once a day and there is a cron job that mounts the drive and runs rsync for the /myth directory (after running mythbackup of course).

Admittedly, if I lose a drive, I may lose one day of files. I can live with that, especially since if I lose a file due to fat fingers, I can recover it.

Allen

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