z/VM Parallel Access Volumes (PAV) and HyperPAV Support

z/VM Parallel Access Volumes (PAV) and HyperPAV Support
IBM System z Technical University – Berlin, Germany– May 21-25
ZVM20: z/VM PAV and HyperPAV Support
Eric Farman, IBM
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
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Notes:
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Performance is in Internal Throughput Rate (ITR) ratio based on measurements and projections using standard IBM benchmarks in a controlled environment.
The actual throughput that any user will experience will vary depending upon considerations such as the amount of multiprogramming in the user's job
stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will
achieve throughput improvements equivalent to the performance ratios stated here.
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All customer examples cited or described in this presentation are presented as illustrations of the manner in which some customers have used IBM products
and the results they may have achieved. Actual environmental costs and performance characteristics will vary depending on individual customer
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© 2012 IBM Corporation
Prices subject to change without notice. Contact your IBM representative or Business Partner for the most current pricing in your geography.
IBM System z Technical University – Berlin, Germany
Agenda
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PAV
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3
Base
Alias
Alias
HyperPAV
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Overview
Configuration
Commands
User Directory
Setup Example
Dynamic PAV
Performance
Overview
Configuration
Commands
User Directory
Configuration File
Documentation
Data
Reference
© 2012 IBM Corporation
PAV
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Overview
z/VM provides support for the Parallel Access Volumes (PAV) feature of
IBM System Storage subsystems.
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With PAV, a real DASD volume is accessed through a Base subchannel
(device) and one or more Alias subchannels
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Volume (represented by Base) shadowed by 1 or more Aliases
Looks like multiple separate, real DASD to host operating system
DASD E100-E102 all access same data
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Base
Alias
Alias
RDEV
E100
RDEV
E101
RDEV
E102
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Overview
z/Architecture allows only 1 active I/O to a single ECKD DASD
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Aliases overcome this restriction providing the ability to have multiple
concurrent I/O operations on a DASD
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Allows higher I/O throughput by reducing I/O queuing
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Control unit provides data serialization
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Each I/O request specifies cylinder range:
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Controller provides shared access for read cylinder ranges
Controller provides exclusive access for write cylinder ranges
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
IOCP Configuration
PAV volumes can be defined as 3390 Model 2, 3, 9 (inc. mod 27 and 54),
or A (EAV) DASD on 3990 Model 3 or 6, 2105, or 2107 Controllers.
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3380 track-compatibility mode for 3390 Model 2 or 3 DASD are also
supported.
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IOCP Statements
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CNTLUNIT
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IODEVICE
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Control units for Bases and Aliases are UNIT=3990, 2105, or 2107
Base UNIT=3390 or 3390B or 3380 or 3380B
Alias UNIT=3390 or 3390A or 3380 or 3380A
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Hardware Console Configuration
The assignment of PAV Bases and Aliases is achieved with the control
unit’s Hardware Management Console (HMC)
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HMC configuration should match IOCP
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Use HMC to initially define which subchannels are Base subchannels,
which subchannels are Alias subchannels, and which Alias subchannels
are associated with each Base
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8
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
VM Configuration
A real Alias subchannel will not come online to VM without an associated
real Base subchannel
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A real Base subchannel must have at least 1 associated real Alias
subchannel for z/VM to recognize the device as a PAV Base subchannel
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Use the Class B, CP QUERY PAV command to view the current allocation
of Base and Alias subchannels
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9
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
VM Configuration (traditional)
PAVs were traditionally supported
by VM (z/VM 5.2.0 and earlier) for
guests as dedicated DASD
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Base and Alias devices could be
dedicated to a single guest or
distributed across multiple guests
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The latter is somewhat dangerous!
Configured to guest(s) with the CP
ATTACH command or DEDICATE
user directory statement
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Only for guests that exploited the
PAV architecture, like z/OS and
Linux
VM Guest A
Base
E100
VM Guest B
Alias
E101
Alias
E102
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10
Data
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
VM Configuration Today (Dedicated DASD)
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Today, a Base and its Aliases may
only be dedicated to one guest
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Base must be dedicated first, all
alias devices can follow
Still configured with CP ATTACH
command or DEDICATE user
directory statement
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For guests that exploit the PAV
architecture
VM Guest A
VDEV 9800 VDEV 9801 VDEV 9802
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Base
E100
Alias
E101
Alias
E102
Data
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
VM Configuration Today (Minidisks)
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z/VM provides linkable minidisks for guests that exploit PAV (e.g., z/OS
and Linux); see illustration next slide
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z/VM also provides workload balancing for guests that don’t exploit PAV
(e.g., CMS)
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Base minidisks are defined with the existing MDISK or LINK user directory
statements (LINK command also supported)
Aliases are defined with new PAVALIAS parameter of the DASDOPT and
MINIOPT user directory statements or with the new CP DEFINE PAVALIAS
command
Real I/O dispatcher queues minidisk I/O across system attached Aliases
Minidisks are defined as in the past; nothing has changed.
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
VM Configuration Today (Minidisks)
VM Guest A
VM Guest B
VM Guest C
VDEV 9800 VDEV 9801 VDEV 9802
VDEV 9800 VDEV 9801 VDEV 9802
VDEV 9800 VDEV 9801 VDEV 9802
Base
E100
Alias
E101
Alias
E102
Data
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
ATTACH Command
When attaching PAV DASD to a guest, the Base must be attached first
before any associated Alias. An associated Alias can only be attached to
the same guest as the Base.
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When attaching PAV DASD to the system, the Base must be attached first
before any associated Alias.
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Aliases can be attached to the system and are exploited for VM I/O if they
contain temporary disk (TDSK) or minidisk (PERM) allocations.
Other CP volume allocations (e.g., PAGE) receive no benefit from system
attached Aliases.
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
DETACH Command
When detaching PAV DASD from a guest, all dedicated Aliases
associated with a particular Base must be detached from the guest before
the Base can be detached.
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When detaching PAV DASD from the system, all system attached Aliases
associated with a particular Base must be detached from the system
before the Base can be detached.
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Minidisk Cache (MDC)
Minidisk cache settings apply to the Base and are inherited by its Aliases
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SET MDCACHE command may not be used with Aliases; results in error
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
DEFINE PAVALIAS Command
Privilege Class G
>>--DEFine--PAValias--vdev--.-----.--BASE--basevdev-------------><
'-FOR-'
The DEFINE PAVALIAS command is used to create new virtual PAV Alias
minidisks. Function can also be accomplished by using the DASDOPT
and MINIOPT user directory statements.
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Newly defined virtual Alias is automatically assigned to a unique
underlying real PAV Alias.
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The command will fail if no more unique real Aliases are available to be
associated with the virtual Alias (per guest virtual machine).
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Query Virtual PAV
Privilege Class G
.-Virtual----.
.-ALL---------------.
>>--Query--'------------'--PAV--+-------------------+-----------><
| <---------------< |
'--.-vdev--------.--'
'-vdev1-vdev2-'
Dedicated Responses
QUERY VIRTUAL PAV ALL
PAV BASE 0290 ON E100 WIL3
PAV ALIAS 0291 ON E101 WIL3 FOR BASE 0290
Minidisk Responses
QUERY VIRTUAL PAV ALL
PAV BASE 0290 ON E100 WIL3 ASSIGNED E100
PAV ALIAS 0291 ON E101 WIL3 ASSIGNED E101 FOR BASE 0290
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
User Directory
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DASDOPT
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Used for Full-Pack Minidisks
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MINIOPT
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Used for Non-Full-Pack Minidisks
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MDISK vdev devtype DEVNO rdev
mode
DASDOPT PAVALIAS vdev
MDISK vdev devtype 0 END volser
mode
DASDOPT PAVALIAS vdev-vdev
LINK userid vdev1 vdev2 mode
DASDOPT PAVALIAS
vdev.numDevs
MDISK vdev devtype 100 50 volser
mode
MINIOPT PAVALIAS vdev
LINK userid vdev1 vdev2 mode
MINIOPT PAVALIAS vdev-vdev
PAVALIAS option of DASDOPT and
MINIOPT statements are used to
create virtual PAV Alias minidisks for a
guest.
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DASDOPT and MINIOPT should
follow the MDISK or LINK statement
associated with the virtual Base.
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DASDOPT and MINIOPT may be
continued on multiple lines with trailing
commas.
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Can have more Aliases in user
directory than exist in hardware.
Virtual Aliases will be assigned in
ascending order until the real
associated Aliases are exhausted.
This will not prevent logon!
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Use DEDICATE vdev rdev for all
dedicated PAV Base and Alias
© 2012 IBM Corporation
devices.
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IBM System z Technical University – Berlin, Germany
Setup example for Linux exploiting PAV minidisks
Base device predefined in user directory:
MDISK 200 3390 DEVNO E100 WR
q pav
Device E100 is a base Parallel Access Volume with the following aliases: E101
Device E101 is an alias Parallel Access Volume device whose base device is E100
attach E100 to system
DASD E100 ATTACHED TO SYSTEM WIL6 PAV BASE
attach E101 to system
DASD E101 ATTACHED TO SYSTEM WIL6 PAV ALIAS
define pavalias 201 for base 200
DASD 201 DEFINED
query virtual pav all
PAV BASE 0200 ON E100 WIL6 ASSIGNED E100
PAV ALIAS 0201 ON E101 WIL6 ASSIGNED E101 FOR BASE 0200
Configure Linux LVM to use virtual PAV Base 200 and Alias 201 as a single logical volume.
For details, see Linux “How to Improve Performance with PAV” whitepaper at:
http://www-128.ibm.com/developerworks/linux/linux390/june2003_documentation.html
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Dynamic PAV
Dynamic PAV is the ability to re-associate an Alias device from one Base
to another
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Guest issued dynamic PAV operation to a dedicated Alias:
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Guest issued dynamic PAV operation to an Alias minidisk:
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Full-pack minidisks only. Otherwise, the Dynamic PAV operation fails.
There must be a unique real Alias available in which to associate the virtual
Alias (per guest machine). Otherwise, the Dynamic PAV operation fails.
Only the virtual configuration is altered. The real Alias to Base association
never changes for minidisks.
Out-board (control unit) initiated dynamic PAV operations:
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Real (and virtual) Alias to Base association will change as long as the new
Base is dedicated to the same guest. Otherwise, the dynamic PAV operation
fails.
All Alias minidisks associated with a real system attached Alias will be
detached from their guests.
A dedicated Alias will behave as if guest issued the dynamic PAV operation.
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Performance
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Dedicated DASD
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Performance metrics for dedicated DASD are solely up to guest virtual
machine; VM issues real I/O as indicated by guest.
Minidisks
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Useful for environments where I/O queuing occurs (see Performance Toolkit
FCX168 report, or equivalent)
Performance gains may be realized only when minidisks are shared among
guests with multiple LINK statements or when multiple minidisks reside on a
real volume
Performance gains are achieved by multiplexing the I/O operations requested
on each guest minidisk over the appropriate real PAV Base and Alias
subchannels
Performance varies depending on controller model and read-write mix
“Law of Diminishing Returns”; defining more Aliases than needed can lower
performance
Success Criterion: Response time equals service time (no wait queue)
For details see,
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http://www.vm.ibm.com/perf/pavmdc.html
http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html
© 2012 IBM Corporation
HyperPAV
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Overview
New feature of the DS8000 (only) that removes the static Alias to Base
binding associated with traditional PAVs
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Alias and Base volumes are pooled per each LSS. An Alias can be
associated with any Base in the Pool; done by host on each I/O request.
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Makes traditional Dynamic PAV obsolete
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VM support for dedicated DASD and Fullpack Minidisks available in z/VM
5.4.0 and later
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Overview
VM dedicated DASD support via
CP ATTACH command or
DEDICATE user directory
statement
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VM Minidisk Support:
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workload balancing for guests that
don’t exploit HyperPAV
linkable full-pack minidisks for
guests that do exploit HyperPAV
New CP DEFINE
HYPERPAVALIAS command
creates HyperPAV Alias minidisks
for exploiting guests
Current exploiters of HyperPAV
are z/VM, z/OS and Linux
(SLES11, RHEL6)
Restricted to fullpack minidisks for
exploiting guests
LSS 010D
Pool 0
Base
4C00
Base
4C04
Alias
4C10
Alias
4C14
Alias
4C11
Alias
4C15
Alias
4C12
Alias
4C16
Alias
4C13
Alias
4C17
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Configuration
HyperPAV Base and Alias subchannels are defined on control unit’s
Hardware Management Console and in IOCP no differently than
traditional PAVs
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HyperPAV hardware, priced feature enables floating Alias function
associated with the HyperPAV architecture for each LSS (logical control
unit)
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Operating system host determines which LSS (logical control unit) is in
HyperPAV vs. traditional PAV mode
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Configuration
A real HyperPAV Alias subchannel will not come online unless a
HyperPAV Base exists in the same hardware Pool.
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A real HyperPAV Base subchannel needs at least 1 HyperPAV Alias in the
same hardware Pool for z/VM to recognize the device as a HyperPAV
Base subchannel.
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Use the Class B, CP QUERY PAV command to view the current
HyperPAV Base and Alias subchannels along with their associated Pools.
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
ATTACH / DETACH Commands
Unlike traditional PAV DASD, HyperPAV Base and Alias devices can be
attached and detached to/from a guest or the system in any order. There
is no Base before Alias (or vise-versa) restrictions.
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HyperPAV Aliases can be attached to the system and are exploited for VM
I/O if they contain temporary disk (TDSK) or minidisk (PERM) allocations.
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Other CP volume allocations receive no benefit from system attached
HyperPAV Aliases.
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Minidisk Cache (MDC)
Minidisk cache settings do not apply to HyperPAV Aliases. Cache setting
are only applicable to HyperPAV Base devices.
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SET MDCACHE command may not be used with HyperPAV Aliases;
results in error
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
DEFINE HYPERPAVALIAS Command
Privilege Class G
>>--DEFine--HYPERPAValias--vdev--.-----.--BASE--basevdev---------><
'-FOR-'
The DEFINE HYPERPAVALIAS command is used to create new virtual
HyperPAV Alias minidisks.
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A newly defined virtual Alias is automatically assigned to a unique
underlying real HyperPAV Alias (in the same real hardware Pool as the
Base).
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The command will fail if no more unique, real Aliases are available in the
real hardware Pool to be associated with the virtual Alias (per guest virtual
machine).
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There can only be 254 Aliases per Pool; and a limit of 16,000 Pools per
LPAR.
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Command currently restricted to Full-Pack minidisks.
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Query Virtual PAV Command
Dedicated
QUERY VIRTUAL PAV ALL
HYPERPAV BASE 0200 ON E100 YAC001 POOL 1
HYPERPAV ALIAS 0201 ON E101 POOL 1
Minidisks
QUERY VIRTUAL PAV ALL
HYPERPAV BASE 0200 ON E100 YAC001 ASSIGNED E100 POOL 1
HYPERPAV ALIAS 0201 ASSIGNED E101 POOL 1
31
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
SET CU Command
The SET CU command is used to set the Parallel Access Volume function
level of each applicable control unit (specified via controller’s ssid).
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Default is either HYPERPAV_allowed or PAV_allowed depending on the
installed capabilities of each control unit.
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HYPERPAV_allowed can’t be set if capability is not available on the
control unit.
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All Alias devices in the specified control unit (ssid) must be off-line when
changing from or to the HYPERPAV_allowed setting.
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Command applies to only first-level VM images; error occurs otherwise.
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New QUERY CU command displays the PAV and HYPERPAV
capabilities of applicable DASD control units.
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.-DASD-.
<-------------<
>>--SET--CU--'------'--.-HYPERPAV_allowed-.---.-ssid------.-----><
|-PAV_allowed------|
'-ssid-ssid-'
'-NOPAV_allowed----'
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© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
User Directory
Use the COMMAND user directory statement with the DEFINE
HYPERPAVALIAS command to create virtual HyperPAV Alias minidisks
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COMMAND statements must appear before all device definition
statements, like MDISK and LINK statements for the Base minidisks
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Examples:
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COMMAND DEFINE HYPERPAVALIAS vdev FOR BASE basevdev
MDISK basevdev devtype DEVNO rdev mode
COMMAND DEFINE HYPERPAVALIAS vdev FOR BASE basevdev
MDISK basevdev devtype 0 END volser mode
COMMAND DEFINE HYPERPAVALIAS vdev FOR BASE basevdev
LINK userid sourcevdev basevdev mode
Use DEDICATE vdev rdev for all dedicated HyperPAV Base and Alias
devices
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Configuration File
The following new system configuration file statements are useful for
managing HyperPAV devices:
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SYSTEM_Alias - Specifies HyperPAV Alias devices to be attached to the
system at VM initialization.
CU - Defines how VM initializes specific control units. Similar to the CP SET
CU command (i.e., sets controller PAV mode).
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Documentation
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CP Command Reference
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CP Planning and Administration Guide
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New and changed messages
Web
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User Directory Statements
Configuration File Statements
“DASD Sharing Chapter” with “Using IBM Parallel Access Volumes” section
CP Messages and Codes
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Command details
http://www.vm.ibm.com/storman/pav/
http://www.vm.ibm.com/perf/pavmdc.html
http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html
http://www-128.ibm.com/developerworks/linux/linux390/june2003_documentation.html
© 2012 IBM Corporation
Fin
Eric Farman
farman@us.ibm.com
z/VM I/O Development
© 2011 IBM Corporation
Reference
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
PAV with Non-Fullpack Minidisks
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Neither z/VM, nor its guest operating systems, could uniquely identify
distinct non-fullpack minidisks
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z/VM 5.4 and later correctly address this problem
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Thus, I/O may inadvertently be driven down an incorrect alias
PTFs available for earlier releases via APAR VM64273
Co-requisite fixes are required for guest operating systems
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z/OS APARs OA22161 and OA25151 are available for z/OS v1.7 through v1.9
Linux on System z: see problem ID 34345 in patch 21 of the October 2005
stream on DeveloperWorks
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http://www.ibm.com/developerworks/linux/linux390/linux-2.6.16-s390-21october2005.html
Included in modern distro's from SUSE and Red Hat
Patches can be applied in stages, but all need to be present in order to
correct this problem.
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Restrictions
A traditional PAV, real Alias may be attached to a guest or SYSTEM only
after its associated real Base has been attached to the same guest or
SYSTEM.
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A tradition PAV, real Base may be detached from a guest or SYSTEM
only if all of its associated Aliases are already free.
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A traditional PAV, real Alias will not come online to VM without an
associated real Base. Also, a real Base must have at least one
associated real Alias for VM (for example, the QUERY PAV command) to
recognize the device as a PAV.
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A real Base cannot be changed or deleted with the SET RDEVICE,
DELETE RDEVICE, DELETE DEVICE, or MODIFY DEVICE commands
unless all associated real Aliases have been deleted with the DELETE
RDEVICE command.
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39
© 2012 IBM Corporation
IBM System z Technical University – Berlin, Germany
Restrictions
CMS does not support virtual Aliases (whether traditional PAV or
HyperPAV). Defining these virtual devices under CMS can cause similar
damage that can be caused by issuing multi-write (MW) links.
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A virtual Alias (whether traditional PAV or HyperPAV) cannot be IPLed.
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PAV Aliases (whether traditional PAV or HyperPAV) can not be used as
VM installation volumes (for example, do not use for the SYSRES
volume).
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VM Paging and Spooling operations do not take advantage of PAVs
(traditional or HyperPAV). It is recommended that PAGE and SPOOL
areas be placed on DASD devices dedicated to this purpose.
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Virtual HyperPAV devices can only be defined as Full-Pack minidisks.
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Diagnoses x18, x20, xA4, x250, and the *BLOCKIO system service do not
support HyperPAV Alias devices since there is no means for specification
of the associated Base. An attempt to do so will result in an error.
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40
© 2012 IBM Corporation
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