I think that LVM/LVM2 is still in it's teen years for the Linux version. LVM2 has made quite a few improvements to the original implementation of
LVM. LVM under AIX allows to do a balance of sorts across the LVM storage units. The biggest thing is that it does give you the ability to
dynamically grow and shrink file systems on the fly. Shrinking those file systems is still problematic under Linux, but it is being worked on. What
LVM in it's basic form doesn't allow you to do is to spread a file across all of the volumes for performance reasons as you add additional physical
volumes to a group. Each file is attached to a specific lun or underlying disk, but the entire file system can grow larger onto the newly added
volumes. Linux LVM doesn't give you that balance function yet, that I know of. That is unless you build the LVM originially with a stripe feature
when you first create it, and that's not a basic implementation or a simple one. Right now I think LVM2 can do a 0 and 1 type striping mechanism and
can be added to dynamically, still being worked on from what I understand. What's funny is that I also have an older TRU64 Unix box here and I've had
the opportunity to work with the older Digital/Compaq/HP LSM (Logical Storage Management) and boy is that system robust. It's too bad that TRU64 is
being killed off for HP/UX. I guess though it does make sense business wise. It's a great storage engine with several optimizations that I see close
ties to my iSeries machines in how they optimize I/O and storage. It gives you the ability to spread data and I/O across multiple luns and has a
great I/O and capacity balance mechanism. The only issue with LSM that I can figure so far is it is so dynamic and can optimize so many possible
things, it makes it very complicated and you can easily mess things up. Which is one of my pet peeves with Linux, you really gotta know what you're
doing when you start messing with tweaking things. I really like the i because it just does that optimization for you, but in doing so it limits it's
flexibility.
Bill Epperson Jr.
Systems Communications Analyst
Memorial Health System
(719) 365-8831
Adam Glauser <adamglauser@xxxxxxxxx>
Sent by: midrange-l-bounces@xxxxxxxxxxxx To
midrange-l@xxxxxxxxxxxx
cc
08/14/2009 10:05
Subject
Re: Explaining single level store to non i people
Please respond to
Midrange Systems Technical Discussion
<midrange-l@xxxxxxxxxxxx>
Nathan Andelin wrote:
Under IBM i, you just pop an additional drive into the bay and the capacity of the DBMS and every file system is automatically extended, no matter
where they may have resided physically. In countless cases, that has been worth its weight in gold.
There is a way to spread filesystems over multiple disks/partitions, for
Linux anyway. The software is called LVM, and my understanding is that
it addresses this issue quite well.
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