Re: Setup XLINK
Software AG - Sitz/Registered office: Uhlandstra?e 12, 64297 Darmstadt, Germany, - Registergericht/Commercial register: Darmstadt HRB 1562 - Vorstand/ Management Board: Karl-Heinz Streibich (Vorsitzender/Chairman), David Broadbent, Mark Edwards, Dr. Peter Kurpick, Ivo Totev, Arnd Zinnhardt; - Aufsichtsratsvorsitzender/ Chairman of the Supervisory Board: Frank F. Beelitz - http://www.softwareag.com -Original Message- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Kris Buelens Sent: Tuesday, March 17, 2009 12:33 PM To: ibmvm@listserv.uark.edu Subject: Re: Setup XLINK XLINK makes it possible to protect multiple minidisks on a shared pack. XLINK checks cylinder ranges. You can test this - on VMA, use LINK userid vdev 1 M - on VMB try LINK userid vdev 1 M and this should fail, CP should tell userid vdev not linked, R/W by VMA Note that there are no commands to dynamically the XLINK definitions as those found in SYSTEM CONFIG, and IPL is required. You don't need to define the volumes as shared, but BEWARE: - The problem is MDC: when MDC is active for a volume, CP may find request data in storage and may no go to the disk fo satisfy an I/O. Hence is an update took place in VMA a request from VMB may read backlevel data - Turn MDC OFF for the shared volumes and you are safe (the default for disks definedd as SHARED) - or, if you know 100% sure that only one system is writing to it - leave MDC ON for the volumes on the writing system - turn MDC OFF for the volumes on all reading systems (my former customer has been working like this for years) 2009/3/17 Berry van Sleeuwen berry.vansleeu...@xs4all.nl: Hello Listers, I am looking into XLINK. The main goal is to be able to determine if a minidiskextent on DASD is already in R/W use on a different VM. This way we could provide for an easy switch for linux guests from one VM to another. We do not setup the full CSE here. SPOOL and DIRMAINT are just for their own VM image. Now I have found that I need: - XLINK_SYSTEM_INCLUDE for every VM system. - XLINK_VOLUME_INCLUDE for every DASD volume. - XLINK FORMAT the DASD to enable the volume for XLINK usage. Do I need more? For instance, it could be that there are multiple minidisks on one volume and that the linuxguests in question are spread across the 4 VM images. Should the DASD be set to SHARED for this? As I understand it linux doesn't require the disks to be SHARED but I'd like to be sure. Are there any other issues I should prepare for? TIA, Berry. -- Kris Buelens, IBM Belgium, VM customer support
Re: Setup XLINK
XLINK makes it possible to protect multiple minidisks on a shared pack. XLINK checks cylinder ranges. You can test this - on VMA, use LINK userid vdev 1 M - on VMB try LINK userid vdev 1 M and this should fail, CP should tell userid vdev not linked, R/W by VMA Note that there are no commands to dynamically the XLINK definitions as those found in SYSTEM CONFIG, and IPL is required. You don't need to define the volumes as shared, but BEWARE: - The problem is MDC: when MDC is active for a volume, CP may find request data in storage and may no go to the disk fo satisfy an I/O. Hence is an update took place in VMA a request from VMB may read backlevel data - Turn MDC OFF for the shared volumes and you are safe (the default for disks definedd as SHARED) - or, if you know 100% sure that only one system is writing to it - leave MDC ON for the volumes on the writing system - turn MDC OFF for the volumes on all reading systems (my former customer has been working like this for years) 2009/3/17 Berry van Sleeuwen berry.vansleeu...@xs4all.nl: Hello Listers, I am looking into XLINK. The main goal is to be able to determine if a minidiskextent on DASD is already in R/W use on a different VM. This way we could provide for an easy switch for linux guests from one VM to another. We do not setup the full CSE here. SPOOL and DIRMAINT are just for their own VM image. Now I have found that I need: - XLINK_SYSTEM_INCLUDE for every VM system. - XLINK_VOLUME_INCLUDE for every DASD volume. - XLINK FORMAT the DASD to enable the volume for XLINK usage. Do I need more? For instance, it could be that there are multiple minidisks on one volume and that the linuxguests in question are spread across the 4 VM images. Should the DASD be set to SHARED for this? As I understand it linux doesn't require the disks to be SHARED but I'd like to be sure. Are there any other issues I should prepare for? TIA, Berry. -- Kris Buelens, IBM Belgium, VM customer support
Re: Setup XLINK
On Tue, Mar 17, 2009 at 12:32 PM, Kris Buelens kris.buel...@gmail.com wrote: XLINK makes it possible to protect multiple minidisks on a shared pack. XLINK checks cylinder ranges. Incorrect Kris. XLINK only protects the starting cylinder. However, as long as magic ensures identical directories, this should be a moot point. You can test this - on VMA, use LINK userid vdev 1 M - on VMB try LINK userid vdev 1 M and this should fail, CP should tell userid vdev not linked, R/W by VMA Note that there are no commands to dynamically the XLINK definitions as those found in SYSTEM CONFIG, and IPL is required. You don't need to define the volumes as shared, but BEWARE: - The problem is MDC: when MDC is active for a volume, CP may find request data in storage and may no go to the disk fo satisfy an I/O. Hence is an update took place in VMA This risk there is when volumes are dynamically added to the sytem, they are per default eligable for MDC. So to play safe you should set MDC OFF if you care a bit about your data. I recall that Perry did some work in the ancient past to do the MDC ON/OFF via ISFC. Berry is looking at Linux disks. In that case there is no legitimate reason to have users read and write at the same time. A few MDC FLUSH in the PROFILE EXEC might be good enough to wipe out trails of a previous incarnation. Bonus points for using PROP to capture the logoff and flush the disks... Rob
Re: Setup XLINK
If you use anything larger than a 3390-3 - I believe you'll need the first 9 cylinders (0-8) reserved for XLINK data. Not too bad if you're just doing the z/VM volumes - some extent rearranging -- but it can be a major effort if volumes with Linux data are included. Scott On Tue, Mar 17, 2009 at 1:56 AM, Berry van Sleeuwen berry.vansleeu...@xs4all.nl wrote: Hello Listers, I am looking into XLINK. The main goal is to be able to determine if a minidiskextent on DASD is already in R/W use on a different VM. This way we could provide for an easy switch for linux guests from one VM to another. We do not setup the full CSE here. SPOOL and DIRMAINT are just for their own VM image. Now I have found that I need: - XLINK_SYSTEM_INCLUDE for every VM system. - XLINK_VOLUME_INCLUDE for every DASD volume. - XLINK FORMAT the DASD to enable the volume for XLINK usage. Do I need more? For instance, it could be that there are multiple minidisks on one volume and that the linuxguests in question are spread across the 4 VM images. Should the DASD be set to SHARED for this? As I understand it linux doesn't require the disks to be SHARED but I'd like to be sure. Are there any other issues I should prepare for? TIA, Berry.
Re: Setup XLINK
Also: for a 3390-9 you can move the CSE area. When you define the volume in SYSTEM CONFIG you can include a parameter that indicates the starting cylinder of the CSE are - this means you can move it to the end of a volume if you want to CSE protect a volume that already has minidisks on it. The XLINK_VOLUME_INCLUDE statement also takes globbed volsers. You can specify VMX* to indicate all those volumes are protected, but beware: CP won't bring a volume online if its volser matches something in the XLINK_VOLUME_INCLUDE list but the volume does not have a CSE area on it. Also - don't CSE protect the first 0-9 cylinders of a VM IPL Volume - the CSE area will overwrite some of the high tracks on cylinder 0 that contain parts of the SALIPL loader. You have to relocate the CSE area to somewhere else on a VM IPL volume. Ask me how I know this... -- Jay Brenneman
