On Friday 22 December 2006 08:50am, John Reiser wrote: > Gilboa Davara wrote: > > Use LVM. > > Trust me. > > You won't be sorry. > > I've been there, done that, and regretted it deeply. > I got rid of LVM the first chance I could. The very first thought in my mind is that you never understood what role LVM plays or how it actually works. By that, I don't mean the internal workings of LVM itself, I mean what LVM does for you and how to take advantage of it. > LVM does not inter-operate with anything else. Bull. LVM takes one or more block devices, aggregates them together into a single volume group (VG) and then manages the disbursement of available storage in the VG by creating block devices called logical volumes (VG). Notice, block devices in, block devices out. It's part of the sheer genius of the design of Linux that the RAID, LVM, multipath-I/O, filesystem "drivers" and other related code doesn't have to know *anything* about any of the other systems. They just work on top of block devices LVM is extremely inter-operable with everything else. > Grub does not work under LVM. There are patches available that let GRUB boot kernel images stored on LVM. But why would you want to? Also, IIRC, GRUB 2 will have this support out-of-the-box. > Parted does not grok LVM: parted doesn't grok a lot of things. In this case, it doesn't need to and shouldn't. parted is a [part]ition [ed]itor. It would be considered inappropriate by many for it to manipulate LVM. That's what the LVM commands are for. But if you want a frontend there is a new on in Fedora/RHEL called "system-config-lvm". SUSE has had extensive LVM support in YaST's partitioning tools for several years. There are frontends available. > you cannot create a hard partition from LVM free space. Nope. But I have no idea what you are thinking here. Not to sound condescending or anything, but that's a completely idiotic thing to suggest. LVM creates block devices that look just like a plain old partition (POP? :) ) to everything that uses them (block devices, partitions, etc.), there is no difference. You can put LVM on RAID on LVM on RAID on iSCSI if wanted to. It's all just block devices. > Using the rescue CDs is a nightmare under LVM: The individual LVM commands are not found in the rescue environment. You have to run "lvm" and then at the "lvm>" prompt you can run LVM commands just like on the normal, running systems. I've wondered why the rescue environment doesn't just have all the lvm commands as symlinks to "lvm", like on the installed systems. That would make it a little easier to use. > the LVM > setup is not recognized automatically Yes, it is. It's always worked just fine as far back as I can remember Red Hat having LVM support at all. I have no idea what you did that prevented it from picking things up. For it to fail, the root filesystem would have to be unavailable or the /etc/fstab file on it would have to be wrong or corrupted (I think that's the whole list). > (you must remember > what it is) and the rescue environment contains no help > or documentation on LVM (such as: the _syntax_ for naming > the pieces!) Sounds like you've only used the stupid names for VGs and LVs that anaconda defaults to, like LogVol00, which are really useless names. > LVM probably kills all low-level backup and recovery. Nope, you're wrong there. IN fact, it has features like snapshotting that make low-level backup and recovery significantly easier and even make it possible to get consistent backups without taking anything offline. Let that DB keep running while you backup it's files (or use it's own backup tool) against an unchanging, read-only copy. > Do not use LVM unless you are 100.000000% certain > that you will never be faced with a hardware disaster. Use RAID (and not linear or RAID0) for redundancy to deal with/weather hardware failures. LVM has nothing to do with improving redundancy. Yes, it does have some striping abilities, very similar to RAID, but that's not what it's for. It's Logical Volume *Management*. Use LVM to make all that space manageable. Don't want to decide right now which "partition" to allocate all that space to? Then don't. With LVM, you can allocate space, *as needed*. Besides, on the few occasions that I have had to deal with hardware failures *i.e. disks and disk controllers), having LVM has been very helpful for me. -- Lamont Peterson <lamont@xxxxxxxxxxxx> Senior Instructor Guru Labs, L.C. [ http://www.GuruLabs.com/ ] NOTE: All messages from this email address should be digitally signed with my 0xDC0DD409 GPG key. It is available on the pgp.mit.edu keyserver as well as other keyservers that sync with MIT's.
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