why LVM to VXVM ?

[Pradep]

Hi Friends,
any thoughts on why someone should convert existing LVM (vxfs) to VXVM ? what existing disadvantage with lvm and what is good to happen if i convert to VXVM ? which is faster ?

administration wise, i think LVM is easy. VXVM has so complex structure and nomenclature of disks and 100s of commands.

what do experts say ?

[Jeeshan · Accepted solution]

Hi

VxVM is good for SAN environments and is not a propriatory Disk manager. Windows will not snuff a VxVM disk when it sees it in your SAN.

VxVM main disadvantage is that it costs $$ to use most of the interesting features. (as does lvm - mirrordisk, online JFS I suppose)


check this link for the comparison of vxfs and vxvm

http://www.sunmanagers.org/pipermail/summaries/2002-September/002449.html

[Ganesan R]

Hi Pradep,

Both products have it's own features and advantages over each other. There are some feature's available on one and not available on other one. Also some feature is available free of cost on one product and priced in other one. Like online resizing, defragmentation, etc

As you said, it depends on the people. On my experience, unlike other flavour of unix most people stick with LVM on HP-UX.

You can google the comparison between LVM and VxVM

VxVM and LVMâ Conceptual Comparison
http://docs.hp.com/en/B7961-90017/ch01s02.html

[Duncan Edmonstone]

>> which is faster ?

others have answered the o0therv questions... for this one - assuming similar volume structures, you will find very little difference at all -0 LVM is probvably slightly faster, but you would be doing well to notice.

If your site has many different UNIX flavours VxVM might be a way of standardising your volumr mgmt dolution across platforms as its available for Solaris, AIX, LinuX, Windows etc. personally I think this advantage is overplayed though - there are still platform specific issues around how you use VxVM.

My default position is use LVM unless there is some specific feature you need that only VxVM provides - e.g. using a cluster filesystem (CFS) the CFS solution for HP-UX only functions on top of the clustered version of VxVM (CVM)

HTH

Duncan

[Steven E. Protter]

Shalom,

I see strengths and weaknesses on both ways to go.

vxvm is a little daunting because I've never used it extensively.

LVM is all the things you say and is the accepted standard on HP-UX. LVM has been ported to Linux which makes it possible to use multi-platform with a couple of cute syntax eccentricities.

vxvm does let you mirror the rootvg with software. Though this is less of an advantage now that most rx class servers ship with hardware mirroring.

I see no reason to learn vxvm and begin using it in production. Thats the opinion of a 10 plus hear veteran of LVM who happily uses it on both HP-UX and Linux.

SEP

[Emil Velez]

VXVM supports a cluster file system with CFS and oracle RAC. When I first took a VXVM course I was impressed at its flexability. It can be very easy to use but it only has like 4 commands (many options) but only a few commands where LVM has about 20 commands.

Base VXVM allows you to mirror your boot disk without any additional license and only the root dg.

vxvm allows you to stripe and mirror and covnert between layered and non layered preserving the data.

Alot depends on what you want to accomplish with your disk mnagement tool.

Speed with

[Armin Kunaschik]

VxVM has some advantages if it comes to reconfigure disks or to online resize LUN's.
Most of this is not necessary for vg00 disk but might be extremely usefull for application volume groups.

The disadvantage is that it's harder to configure and, in case of a disk failure, causes higher I/O on the system.

The biggest disadvantage is, that it's very hard to recover from a boot disk failure if the system was rebooted.

So my advice is not to use VxVM on boot disks! Depending on your needs it's ok to use VxVM for application disks. But since you have to pay additional licenses for every little feature you should think carefully.

My 2 cents,
Armin

PS: Please assign points if you find answers useful!

[Doug O'Leary]

Hey;

My current client has had this discussion any number of times. Vxvm is, from a straight technological viewpoint, a superior product. It enables dynamic multipathing, online reorganizations, and, after you get used to it, is as easy to manipulate as LVM. There are other advantages, but those are the ones I run into the most often.

As pointed out, though, it's not free. In fact, from what I've seen, Veritas (is it symantec now?) seems to like it quite a bit.

I like vxvm for it's flexibility; however, I have *yet* to see a situation that requires vxvm over LVM. While you can't have a dynamic balancing of load across channels using pvlinks, you can certainly balance them manually.

Probably the closest I've seen to the requirement is when a request came to extend a 4-way striped logical volume when I've only had space on two disks. Vxvm would be able to support something along those lines, situationally dependent, by using the online reorg. That's happened, what, three times over four years? Possibly not something that would justify the cost.

I whole-heartedy support the suggestion *NOT* to encapsulate the root disks as well. That's just asking for trouble. Sun has only recently (last few years?) gotten to the point where encapsulating the root disks doesn't automatically cause patching problems. Sun and vxvm have been partnered for decades. HP's use of vxvm doesn't nearly cover that same time frame - and LVM is much more tied into the system architecture than disksuite ever was for solaris. If you want to use vxvm, use it for your data volumes - not the OS.

Doug O'Leary