Jeff Simpson wrote:
yes - it writes unique identifiers to each drive.Lots of other people responded, but I need to add my 2 cents. There
is nothing unreliable about LVM. I've used it on many production
servers, many people use it for their MythTV system. You just don't
have it configured correctly. Have you read the LVM HOWTO? It's very
useful and easy to find on google, it may be included with your LVM
install.
That part about LVM that I'm curious about (and anyone who knows this, feel free to chime in) is what happens when you want to remove / move a drive?
If I accidently put the drives back in my system in the wrong place (for example, hdb and hdg get swapped), does LVM know which partition goes where?
I suggest that when you set up a system like this you rehearse various failure scenarios - force an error and do a resync with raid, add a PV to an LVM VG, grow the filesystems, swap disks etc etc
Then, should the worst occur you have at least typed in the commands...
it knows. (it scans all devices for tags and reassembles the LV intelligently)is there a way to tell it which drives should be in the volume group if they change without having to re-create the whole thing?
(obviously if I remove a drive with data on it, it will messno - it won't mess up - it just tells you that a drive is missing.
up, but if I swap around a few of them or put them at different device
labels, can LVM be trained about the change?)
(of course, until you replace the drive you won't be able to access it - and here isn't the place to go into emergency recover scenarios - but they exist)
To answer your question...I really like the idea of LVM, and I especially like having a single partition made up of three 160 gig drives - but I'm worried about what might happen if any of those three drives needed to be moved, removed, etc. Do I automatically lose all my data
First, if any one of the drives failed you'd probably lose all your data (so if I had those 3 drives, I'd have a 320Gb raid5 array and feel safe that if I ever lost a disk then my data would be OK)
If you just moved a drive eg from one channel to another it'd be fine - you'd never notice.
If you removed a drive without warning the LV would just refuse to mount until you put it back - then it'd be fine.
If you wanted to remove one you'd have to shrink your filesystem to 320Gb (ext3 and reiser can do this, xfs can't, jfs I don't know)
Then you'd deallocate the drive and remove it.
HTH
David
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