Linux LVM - Is It Ready for Prime Time? 62
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?"
LVM on AIX rocks. (Score:4, Informative)
Re:LVM on AIX rocks. (Score:1)
Re:Linux LVM (Score:3, Informative)
Re:Linux LVM (Score:5, Funny)
So the poster will be able to replace his costly IBM hardware with free IBM software. If that's not ironic, I don't know what is.
Re:Linux LVM (Score:2)
Well, I suppose it is proof positive that IBM is in two business: Support, and Hardware.
Why the pricey replacement drive? (Score:3, Interesting)
Odds are the drives are OEM versions of a very popular drive vendor, perhaps pop it out, figure what kind of drive it is, buy a new one that is an exact match (or better yet, buy five new ones of exactly the same type) and replace them yourself for +/- $2,000 total) and restore from your backup. Maybe this is a little oversimplified but if it is a RS/6000 box odds are it uses regular ol' SCSI drives.
Re:Why the pricey replacement drive? (Score:4, Informative)
Re:Why the pricey replacement drive? (Score:1)
As far as I can tell, Sun doesn't do this, at least. I installed a Seagate U320 SCSI drive into a Sun Ultra workstation--it works beautifully (only at 40MB/sec, now). Most of the Sun-branded drives are really just certified model numbers of Seagate, IBM, Fujitsu, or, historically, Conner drives.
Re:Why the pricey replacement drive? (Score:2)
EMC changes the firmware in their drives which look a lot like Seagate ones. But honestly, would you even think about putting an off-the-shelf-drive into an expensive EMC box?
Sun has firmware updates for their disks in T3 storage arrays. I would not expect any problem, but i don't want to find out that the T3 completely crashed after a firmware update of the drives, just because one of the drives had a small bug in the firmware which prevented it from being updated correctly.
Quite often, while it's techni
Re:Why the pricey replacement drive? (Score:3, Informative)
Re:Why the pricey replacement drive? (Score:2)
In any case, I wouldn't risk replacing the actual disk within the mounting hardware, even if it were fairly simple. The attached hardware is just too expensive to risk f
Re:Why the pricey replacement drive? (Score:2)
Using disks from the same batch, from the same manufacturer (which is what comes to my mind when you say an "exact match") for a RAID setup, pretty much goes against every decent thing I've read about and learned through the years.
The general reason being that once a disk in a batch goes down, so shall the other disks in the same batch go down pretty soon too, thus increasing the risk of having more than one disk down (thus potentially losing data).
Use disks from different batches. Hell
Re:Why the pricey replacement drive? (Score:2)
However, if the drives he has are 3+ years old and have been running for three years straight, only now starting to see failures - that sounds like a pretty good batch to me.
Unless they are on the far-side of the bathtub shaped curve (drive mortality is very high at the very beginning, and at the end of the expected life cycle
LVM and Redhat 7.3 (Score:5, Informative)
just my 2 cents.......
Re:LVM and Redhat 7.3 (Score:1)
About a year and a half ago we setup a 6450 with fiberchannel and lvm. It is still running good.
Re:LVM and Redhat 7.3 (Score:2)
non-production use (Score:1)
YMMV, however, as neither one of these boxes is heavily loaded and I've never required the functionality on any of my production servers..
Re:non-production use (Score:2)
--As far as LVM being "ready for prime time" - well, it works - altho I haven't had to deal with a drive failure yet. It doesn't have a decent free frontend (ncurses) interface unless you use something like SuSE's LiveCD (yast) to set things up.
--BTW, I recommend using Reiserfs over LVM. Just my experience.
Re:non-production use (Score:1)
Re:non-production use (Score:2)
Yeah, sort of. (Score:3, Interesting)
But, it's looking as if the LVM code isn't actually included in the 2.5/2.6 series of kernel (I could be wrong). If you plan on upgrading to this eventually, stay away from LVM. If you don't care just dive in.
Re:Yeah, sort of. (Score:2)
The server will serving home file systems, so there will be no "norm" for usage patterns. I like that reiser lets you grow filesystems on the fly. But is it as solid as ext2/ext3?
Re:Yeah, sort of. (Score:1)
There are four gotchas with XFS, though:
First, while you can grow an XFS filesystem, you can't shrink it. You have to backup and mkfs.
Second, if you lose power between writing metadata and data, you can end up with a partially empty file. Since I know you'll hav
Re:Yeah, sort of. (Score:2)
Well, you live and you learn, I guess RAID really is the way to go for storage. (Even at home.)
Re:Yeah, sort of. (Score:1)
Re:Yeah, sort of. (Score:1)
Improving ext2/3 data streaming to disk (Score:2)
I had similar problems with IDE disks and ext2/3. You need to alter the bdflush settings in /proc/sys/vm.
Try:
echo "5 150 0 50
Funny? Flaimbait? -- YOU DECIDE! (Score:5, Funny)
Well, according to SCO, the LVM support in Linux was added by IBM, so it's probably pretty good.
(/me ducks)
Re:Funny? Flaimbait? -- YOU DECIDE! (Score:1)
if you liked the aix volume manger, try evms (Score:1, Redundant)
Linux LVM just works for me (Score:4, Informative)
The only thing that scares me about Linux LVM (Score:5, Interesting)
is that they keep replacing it and reimplementing it in the kernel.
The one linked to in the article (Sistina's) is in 2.4. I'm using it at home, and I like it. We're considering using it at work, but I hear rumours that 2.6 will contain Something Completely Different (Again), which annoys me.
Re:Could someone explain to me? (Score:2)
LVM also allows you to dynamically add and remove storage to a single filesystem.
Re:Could someone explain to me? (Score:5, Informative)
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.
Journaling file system vs. LVM (Score:2)
Re:Journaling file system vs. LVM (Score:1)
Re:Journaling file system vs. LVM (Score:2)
In any event, the filesystem layer is last layer you apply -- it is totally separate from either MD or LVM.
So, no, LVM and MD don't have anything to do with journaling. That's the filesystem's job. In RH9, the only journaling filesystems are ext3 (available in the
Different approach (Score:1)
I was wondering if we could switch the approach slightly.
All underlying fs seems good on paper and all seem to have strong/weak points depending on the view/desired usage.
Since there's no solution that fits it all (speed, reliability, price etc) under all possibile scenarios lets try to focus in a particular one.
I have a server for which I can have small downtime If I need to replace a defective drive, but can not tolerate to loose data or extensive fsck if for some reason it locks up.
So, since hard
LVM? (Score:1)
Re:LVM? (Score:2)
Also able to do snapshots, etc.
Re:LVM? (Score:1)
Good experience with EVMS (Score:2)
Linux LVM is ok, but some caveats (Score:4, Informative)
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
Re:Linux LVM is ok, but some caveats (Score:1)
I'm using it in several places (Score:2, Interesting)
The mail spool for a 15k-user ISP in southwestern Ontario is running on Slack9 + LVM (Reiserfs). It exports the spool via NFS and the edge servers (SMTP+IMAP4+POP3, virus+spamscan) mount the spool directly over ipsec. No issues. I can grow the filesystem, take snapshots and it all just works. The PostgreSQL database is also on an LVM volume, but I haven't had to do much with it related to LVM yet, as pg_dump works live.
I have a number of other mail spools for businesses around the area (probably a hal
Hot Swapping? (Score:3, Insightful)
With good hardware, you can walk up to a running machine and replace the failed drive then and there. Hopefully your 144Gb raid-5 array has been fully rebuilt by the time you come back from lunch. If you don't have hot-swap hardware, you have to schedule downtime, come back later that night, shut it down, pull the drive and pop in a new one. And hope everything powers up OK, cos if the power supply stuffs up at that time of night and you don't have a (good) support contract you are going to have a lot of fun getting everything going again before the rest of the office shows up for work.
I know you can get hot-swap IDE hardware these days, but I've never used them. I suspect hot-swap IDE drives are not that much cheaper then SCSI, but I could be wrong.
One last little bit of advice, try including a hot spare in your array. Its nice to come in in the morning and read an email saying that a hard drive failed last night, and the array was automatically re-built using the spare before start of business. If you are going to go with non hot-swap hardware, Iâ(TM)d say this is a must. Running raid-5 in degraded mode is no fun.
Re:Hot Swapping? (Score:2)
I have one of the (lower end) 3ware ide-raid cards, and they claim to support hot swap. You have to use their admin tool to tell the controller to deactivate the drive, but supposedly you can
Re:Hot Swapping? (Score:2)
Sure opening the case and using a screwdriver isn't as much fun, but its also risky. With a proper enclosure there is much less change you are going to stuff something up. Thats why server
Filesystem growing is missing (Score:1)
Re:Filesystem growing is missing (Score:1)
Re:Filesystem growing is missing (Score:1)
Prove it. Give a command that can do it, or something. I certainly don't know of a way, unless something changed in the past couple months.
Re:Filesystem growing is missing (Score:3, Informative)
lvextend to increase the volume.
resize_reiserfs to increase the filesystem.
Only works if you want to increase the filesystem, not shrink it.
I should hope so (Score:2)
The 30 RH desktops I've installed have
I used it on redhat 7.3 (Score:1)
LVM (Score:2)
Mmmm... tasty striping.