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Linux LVM - Is It Ready for Prime Time?
Deagol asks: "I'd like to replace our aging IBM server with a commodity solution (Linux, 3Ware cards, and lots of IDE drives). The main reason is price (the cost of 5 36GB SCSI disks for this sucker -- one of which died today -- could pay for the replacement server with 2TB of usable space after RAID-5. Being a huge fan of AIX's LVM,I've recently been playing with the Linux version of LVM. It's got all the right features (and even the ability to shrink logical volumes, a feature which AIX 4.3.3 doesn't have!), though the commands aren't as polished as the AIX counterparts. The big question for me is, will it stand up and be stable under heavy load, like the IBM does? Is anyone running Linux LVM on a 1TB+, 24/7 production machine?"
For those who haven't used it, the LVM support on AIX is probably the best in the industry. It allows you to do just about anything, in a very clean, structured (if somewhat hard to figure out at first) way. I personally have not used it on Linux, so can't comment on the poster's main question, but the kernel-raid stuff is not up to part with IBM's LBM.
"He who would learn astronomy, and other recondite arts, let him go elsewhere. " -- John Calvin, commenting on Genesis 1
I think that was EVMS, not LVM. EVMS was a potential IBM replacement for LVM, but was rejected by Linus.
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I built LVM into a RH 7.3 kernel and used it for a DB2 database box. Worked great with the dell 2650 and a 1 tb powervault 220s (raid5 ...aaarrrg...) with the perc3 raid controller. It passed our rather aggressive load testing cyle, ~7 days constant load w/ a variety of different tests, (broken queries, massive table joins, etc, stuff you WOULDN'T want to see in production) and passed with flying colors. It remained in production for a little under a year until we migrated to a Oracle on Linux solution w/o LVM (RedHat AS2.1). I'd do it again in a minute if the implementation called for it.....
just my 2 cents.......
I have been using LVM on my workstation and just about every machine that I have built in the past 2 years. I also use AIX everyday and agree that the LVM is very robust but I prefer the simplicity of the linux LVM.I recently built a box with software raid 0 and made the whole thing on physical volume and have had zero problems. I have also user the LVM to migrate date from one dist to another without any problems. Oh and did I mention that the LVM howto is really really easy to understand even if you have no previous LVM experiance.
Don't be surprised if that doesn't work. I'm not sure about IBM, but in some cases the storage vendor installs custom firmware on the drives. If you install a different drive in the system, it might not behave correctly.
(cough) Have you ever priced an IBM SSA drive? Scsi it's not. We're running many many terabytes of Shark storage here, most of which is attached to either the Mainframes or the SP complexes, and the cost of a 36GB or 72GB SSA drive are STAGGERING.
As far as stability and reliability goes, I haven't experienced any problems yet.
/boot has to be a non-LVM partition. I'd recommend making a root filesystem of a few hundred megs, outside of LVM. It's less of a hassle than making a separate /boot filesystem outside of LVM.
... etc.) but if you're used to AIX LVM, you'll be up to speed with this in no time.
There are some features though that are still missing from Linux LVM, compared to AIX LVM. One of them is mirroring on the logical volume level (no mklvcopy command). You can sort of get around this by creating a software raid device, and then make it a physical disk. Or even better: just go for a hardware RAID(1/5) solution.
Another thing to keep in mind is that, unlike in AIX, you can't put *all* filesystems in LVM. Either the root filesystem or
Also if you want to be able to resize live filesystems, you have to be careful about your choice of filesystem. Reiserfs for example supports online resizing, while ext3 doesn't (yet?)
All things considered Linux LVM is a great addition to Linux, but it's not as nicely integrated yet as AIX's LVM.
One final thing to note is that the Linux LVM commands seem to be modeled after HP-UX LVM rather than AIX LVM. (e.g. lvcreate instead of mklv, vgdisplay instead of lsvg
The underlying hardware of the replacement box is 16 180GB IDE drives, split between 2 8-port 3Ware cards. Each card is doing RAID-5 with 7 drives, the 8th being a hot spare. I let the hardware manage the redundancy for me.
Linux actually sees 2 1080GB (~1TB) SCSI drives. Using standard methods, I can partition these 2 drives any way you normally can under linux. But that kind of binds my feet.
For example, what if the 500GB filesystem for Group A is full and they're clamoring for more space? Using standard partitioning, I'd have to create another larger filesystem, copy the data over, re-export the space, then finally re-claim the old filesystem. In addition to being a pain in the ass, this would require a down time for the users. However, using LVM, I can simply append more of those "chunks" I mentioned above, without creating a new filesystem, Better yet, I can do this on a live system -- my users won't notice a thing (other than the sudden appearance of new file space).
It's really cool stuff.
I'm still uneasy about the reliability, though. I have no hesitation about resizing on-the-fly with hundreds of people running batch jobs on the filesystem under AIX. I haven't seen enough of the Linux LVM in action yet to be that confident of its abilities. If anyone can comment on how Linux NFS and Samba handle having the underlying filesystem resized on-the-fly, I'd love to hear about it.
Method of processing duck feet
Been around pretty long.
lvextend to increase the volume.
resize_reiserfs to increase the filesystem.
Only works if you want to increase the filesystem, not shrink it.
Je ne parle pas francais.