file duplication (raid?) and adding more disks - difficulty?

[dpkform]

I am considering moving from my Windows Home Server to Amahi, but am concerned about the potential end user complexity of managing/adding physical drives.

One of the two greatest benefits of WHS is super easy management of adding/removing drives (the other being hands-off nightly automated PC backups). I can select which shared folders I want to have duplicated on two physical drives. I can add drives, and remove drives (space permitting) through the GUI, with a couple simple clicks. WHS uses a process called Drive Extender (DE) to manage this.

The reading I have been doing seems to suggest similar things are possible on Amahi with "LVM" but it appears the process is vastly more complicated, and administered directly in the OS and not through Amahi. Also, the examples I have read about "adding" storage space to a RAID 1 LVM partition, specify REPLACING existing smaller hard drives with larger ones. Is it not possible to simply add additional drives, and keep existing drives?

http://linuxdevcenter.com/pub/a/linux/2 ... tml?page=4

The major downside to WHS DE is its closed and mysterious nature. At the user level, all data it gathered into a single "D" drive volume, although it is actually distributed among drives. I have found DE to be at times a very sloppy, problematic solution. At the moment, my 1.78 TB system should have 300GB more free space than is currently shown in WHS. No one on the WHS forums can explain why this is happening, or how to free up the space - which by searching the drives themselves, or simply adding the per category storage totals on WHS, SHOULD be available as free space. If you want more detail, here is my post on the MS WHS forums.

http://social.microsoft.com/Forums/en-U ... 83d51efb51

Now the positive to this negative experience with WHS, is that while I have lost what should be a large chunk of available free space, I have not lost any files in folders where I have duplication turned on. I recently had my system drive crash, and while I did have to completely re-install the system (no drive redundancy possible on system partition) my duplicated files were maintained. Actually, I also lost all my PC backups - as WHS does not natively support disk duplication for PC backups. Fortunately though, I had used a WHS add-in called BDBB to manually create a backup of my PC backups, to an external drive, and was able to restore my PC backups that way.

My hesitation with moving to Amahi is that if Raid 1, and LVM is not supported within Amahi itself, that I may wind up losing data through my own user error, by perhaps not properly setting things up. I am also concerned about the ability to add additional drives, rather than replacing existing smaller drives, and perhaps screwing things up when I try to do so. Finally, even if I do everything right, what I have read seems to indicate that recovering from a hard drive crash, especially if the system volume is on LVM, can be a difficult, or at least complicated process. Is there an easier, more direct way to manage storage space, duplication, adding/removing drives within Amahi?

Many Thanks !

edit: PS - I should add, that I do have a basic understanding of partitioning disks, and have regularly done so within Windows, even using some command prompts in the past. I have also installed Ubuntu and used the partitioning system in the installation GUI. My basic experience while it may be helpful, has also taught me how dangerous a single mistake can be!

[moredruid]

to answer your last question first:
RAID/LVM recovery is very _very_ hard in Linux. I've seen this question asked to Linux gurus (e.g. Klaus Knopper, creator of the Knoppix distribution) and they inevitable give the same answer: You're better off with hardware RAID or fakeRAID (semi software RAID as found in the BIOS of more recent mainboards).

The problem with RAID recovery is that there are so many ways to set up software RAID in Linux (for just as many scenarios, each with say 5 different ways of failing) that it's very difficult to tell exactly how to recover. If there were "one true way" (TM) of doing this it would be easy and a nice front-end would already exist.

as to adding new disks and keeping the old ones: Of course that's possible. If you're using LVM it's also possible to add the new disk to your storage pool. It's not (yet) easy, however I might be able to cobble a script together that can do the hard stuff (oohhh cpg is going to be on my tail now ) automatically for you. There's only 1 real requirement for that, and that's that you have setup a volumegroup and logical volume for /var/hda/files during the install of the system. This could be added to the installation tutorial for advanced setups I guess but it's not that easy.

[dpkform]

Thanks for the quick reply. I just checked and surprisingly my ultra cheap Gigabyte GA-MA74GM-S2 motherboard, with AMD 740G - SB 700 chipset DOES support RAID.

The documentation in the motherboard manual, however, is EXTREMELY sparse. Raid 0 setup is the example given, and of course for reliability I would want RAID 1 I believe. No documentation on how to know if a drive in the raid pair has failed, or what to do when that happens. That's not re-assuring to a RAID noob like me. RAID is supposed to lessen my worry - not add to my worry

The manual does indicate that drivers are required for Windows operating systems older than Vista. A quick check of AMD's and Gigabyte's websites, show no drivers are offered for Linux, the only drivers available are for Windows OS.

Would Debian need a driver, to interact with a raid 1 configured on my motherboard?

edit - also - I assume that if I was able to configure RAID on my motherboard, that each RAID 1 drive pair would show as a single drive to Debian, and that I could then use LVM to create drive-spanning volumes. Is this correct?

Windows Home Server also offers a backup feature that allows backup of data to an external drive. An add-in also allows backups of computer backups to an external drive. That drive then of course be stored at a different physical location. I became so disgusted with WHS, that I just did a fresh clean install, wiping all my server hard drives. At the moment, I am restoring the data to my server, from my external drive. It will be interesting to see, if WHS will then properly account for the free space on my drives.