LVM and SAN LUNs

[Dave Thompson_5]

Should LVM be used for a group of LUNs presented to HP-UX from a CASA SAN?

What are the advantages/disadvantages of configuring SAN LUNs into LVM volume groups?

It seems to me that creating a LVM volume group from a bunch of SAN LUNs adds an additional level of complexity that isn't really necessary. Once the LUNs are part of a volume group, it looks like I loose the ability to manage those LUNS individually at the CASA level (point-in-time snapshots, mirroring, etc.). Rather, I have to treat all LUNs belonging to a VG as a single entity.

By simply mounting the disks in HP-UX as individual JFS disks, do I loose anything? Alternate HBA paths, etc.?

Thanks in advance for your insight.
Dave

[Curtis Wheatley_2]

I would suggest that LVM be used for management of the luns. The SAN portion is really for the device management of the storage subsystem. LVM is used for the creations of logical volumns & file systems. The point-in-time & mirroring can still be utilized quite well by HPUX. When you do a point-in-time backup of a lun you will need to do a vgchgid to the new lun before you can bring it in as a new volumn group. The vgchgid man pages will assist you in the process. The mirroring the san provides isn't really lost as it's used for reduction of SPOF within the array frame. Please advise if I can answer some additional questions for you.

[Mark Grant]

Well, as HPUX can't cope with resizing a LUN you will lose the abiity to increase or decrease filesystem sizes online.

[Ashwani Kashyap]

Yu should use LVM to manage the LUNS from the host side . Its pretty easy to manage and very flexible .

And you don't really loose any SAN level control of the LUNS . YOu can still take all the snapshots , array level mirroring with no problems except whne you resize the LUN . HPUX cannothandle that .

But otherwise you don't loose anything not even alternate level HBA patch .