I'm in full agreement here. I haven't used LVM under Linux, but I have used it *extensively* AIX v3.x and v4.x on a couple of previous jobs. As mentioned below, it works great for databases and large servers. Came in handy for DB2 and one of my servers with 4k+ users.
--Reggie On Wednesday, July 23, 2003 9:46 PM, [EMAIL PROTECTED] <> wrote: > For those of you who are just getting into Linux, or those who have > been at it for awhile but haven't yet gotten their hands dirty in LVM, > I think it is time for a quick intro. > > Those of you who hang out in the #trilug channel on IRC heard me > asking some questions earlier, then finding the answers and becoming > quite enamored with this completely underexposed part of most modern > Linux distributions. > > LVM, or Logical Volume Management, is a software tool that allows you > to abstract and manage your hard disk(s). It has undeniable perks for > small standalone servers with a single IDE disk as well as large > enterprise servers with multi-terabyte SAN arrays. > > First you need to wrap your brain around how LVM organizes your disks. > First you take entire hard disks, or partitions of hard disks, and tag > them as a Physical Volume (PV). > > Next you create a Volume Group (VG) which can contain one or more > PV's. You can think of the VG as one large virtual hard disk. > > The next step is to create Logical Volumes (LV). An LV is like a > partition of a hard disk. One or more LV's are contained within a VG. > You don't have to use all of your available space, and indeed you > probably shouldn't use up all of your available space when creating > LV's. > > The LV's are formatted with the filesystem of your choice (usually > ext3) just like a normal hard disk partition. They can then be > mounted like a normal filesystem. > > But then it gets neat. > > Let's say your /home partition gets close to filling up. Remember how > you didn't allocate all of your available space when making up the > LV's? Well now you can extend your LV that contains /home, and extend > the filesystem itself to consume the additional space in the LV that > you just appended. > > What if you *did* use up all of your available space when you defined > your LV's? Not a problem. Chances are one of your other filesystems > has free space. Let's say /usr has 2GB of free space. /usr doesn't > change much. So let's shrink the LV that contains /usr by 1800MB and > then reallocate that space to /home. Not a problem. You can shrink > filesystems just as easily as you can grow them. > > For you RDBMS admins check this out; you can create filesystem > snapshots using unallocated space. So you can stop the database, > create a snapshot, and start the database again in a second or two. > Then just back up from the snapshot, and disable the snapshot when > you're done. Total RDBMS downtime is so fast you might miss it if you > blink. > > You can read the LVM HOWTO at > http://tldp.org/HOWTO/LVM-HOWTO/index.html but really the only way to > get an appreciation for LVM is to slap an extra old drive or two (or > three) into your Linux box and play with it. I did just that today > and came away salivating from the practical applications of this. > And this is someone who has been using Linux professionally for over > five years. > > The commands are very easy to understand. If you have figured out how > to edit a file in vi or emacs, then you have enough brain cells to > understand the simple management commands for LVM. > > For you install fest folks, you might want to give serious though to > making use of LVM in your installs. It will give the owner of the box > a lot more control over disk layout down the road when they understand > the dynamics of their machine better and can re-allocate space as > needed (or append new drives even). > > I know that Red Hat 9 has LVM support in the installer, and I am told > Mandrake has had this for some time. Older versions of Red Hat don't > seem to have full support for this, and by extension some of the Red > Hat offshoots don't seem to yet. The HOWTO describes, well, HOW TO > install LVM on systems that don't already have it. -- TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug TriLUG Organizational FAQ : http://trilug.org/faq/ TriLUG Member Services FAQ : http://members.trilug.org/services_faq/ TriLUG PGP Keyring : http://trilug.org/~chrish/trilug.asc
