Here's what we were told: Without NPIV, the FCP CHPID acts like a shared HBA, and all LUNS are visible to all virtual machines in all LPARs. Only one OS instance can use a given LUN, however. If another tries, the LUN will appear busy.
WITH NPIV, the system assigns an arbitrary virtual WWPN to each individual address (device number/subchannel). On the storage side, the SAN admins map/mask/whatever to the virtual HBA port names. The LUNs can be mapped to multiples, so sharing LUNs is possible. To share tape drives between zLinux instances for TSM server, NPIV is required. For us, this whole business of arbitrary virtual port names has serious DR implications. That, coupled with the whole business of having to code specific WWPNs in zfcp.conf, has caused us to proceed very slowly with FCP devices in general. -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of Richard Troth Sent: Tuesday, June 05, 2007 1:09 PM To: LINUX-390@VM.MARIST.EDU Subject: [LINUX-390] FCP - shared disk [was: RHEL 4 - FCP - tape drives] Sir Alan spake: > NPIV has nothing to do with sharing across LPARs. > Sharing is simply a matter of giving an multiple LPARs > access to different subchannels the same FCP chpid. I was thinking the same thing, however ... Your SAN team may need to zone or mask things differently if multiple LPARs have access to a device and you're not using NPIV. Case in point for me is one volume (one LUN, a disk) that I need to share across five VM systems, each in its own LPAR, one physical box, one CHPID (per path), one WWPN (per path). The host presents one entity to the fabric, without NPIV, so when I (try to) bring the volume on-line in another LPAR, it fails because it is busy. I don't know SAN fabric capabilities well enough to know if this is supposed to work without special tricks, or without them, or at all. I suspect that with NPIV it will work except that our SAN team would have to zone the LUN to multiple hosts. (But we want to do that eventually anyway.) It stretches the whole disk sharing thing beyond System z and z/VM and lets Sun, HP, AIX, and the rest enjoy the pain. This is disk, not tape, if that matters. -- R; ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -------------------------------------------------------- This message w/attachments (message) may be privileged, confidential or proprietary, and if you are not an intended recipient, please notify the sender, do not use or share it and delete it. Unless specifically indicated, this message is not an offer to sell or a solicitation of any investment products or other financial product or service, an official confirmation of any transaction, or an official statement of Merrill Lynch. Subject to applicable law, Merrill Lynch may monitor, review and retain e-communications (EC) traveling through its networks/systems. The laws of the country of each sender/recipient may impact the handling of EC, and EC may be archived, supervised and produced in countries other than the country in which you are located. This message cannot be guaranteed to be secure or error-free. This message is subject to terms available at the following link: http://www.ml.com/e-communications_terms/. By messaging with Merrill Lynch you consent to the foregoing. -------------------------------------------------------- ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
