Flash Express feature
This appendix briefly describes the optional Flash Express feature of the z13, z13s, zEC12, and zBC12 platforms. The following topics are covered in this appendix:
Replacement of Flash Express
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Note: Starting with the IBM z14, Flash Express (FC #0402 and FC 0403) was replaced by Virtual Flash memory (VFM). VFM implements Extended Asynchronous Data Mover (EADM) architecture by using HSA-like memory instead of Flash card pairs.
The VFM features are available in the following sizes:
•For z14, one VFM feature is 1.5 TB (FC #0604). Up to four features per system can be ordered.
•For z14 ZR1, one VFM feature is 512 GB (FC #0614). Up to four features per system can be ordered.
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Overview
Flash Express is an innovative, optional feature that is available on z13, z13s, zEC12, and zBC12 servers. It improves performance and availability for critical business workloads that cannot afford any reduction in service levels. Flash Express is easy to configure, requires no special skills, and provides rapid time to value.
Flash Express is internal storage that is implemented with solid-state drives (SSDs) mounted in PCIe Flash Express features. Flash Express features are ordered in pairs for availability. A pair provides 1.4 TB of storage. A maximum of four pairs are supported in z13, z13s, zEC12, and zBC12. Flash Express storage is allocated to each partition and is similar to main memory allocation. The allocation is specified at the Support Elements (SE) or Hardware Management Console (HMC).
The IBM z/OS operating system uses the Flash Express feature as storage-class memory (SCM). The Coupling Facility Control Code (CFCC) can also use Flash Express as SCM. For the CF, flash memory provides a standby capacity for use by IBM MQ shared queues structures. This technique provides protection against transient backups in the shared queue from causing the structure to fill up.
Flash Express provides immediate benefits. It is used by the real storage manager (RSM) for z/OS paging and supervisor call (SVC) memory dumps. It reduces processor cycles from paging and improves availability by reducing SVC memory dump duration due to page-in of AUX storage. The value of Flash Express is not in replacing memory with flash, but replacing disk with it. It provides support for pageable large pages (1 MB). If contiguous flash space is available, pageable large pages are preferentially written to flash. If available space exists on both flash and disk, makes a selection that is based on response time.
The Flash Express feature (0403) on z13 (new build), z13s, and (0402) on zEC12, and zBC12 with CFCC level 19 or later is used as a resilient solution for overflow of IBM MQ shared queues in the coupling facility. This new function allows list structure data to be migrated to Flash Express memory as needed. It is needed when the consumers of data do not keep pace with data creators for some reason, and then migrate it back to real memory to be processed.
Flash Express
Flash Express is supported on z13, z13s, zEC12, and zBC12 servers:
•The Flash Express feature occupies one I/O slot in a PCIe I/O drawer.
•The Flash Express feature is always installed in pairs. The minimum order is two features and the maximum order is eight features, in increments of two features. A maximum of four pairs (4 x 1.4 = 5.6 TB) are supported in a system.
•One PCIe I/O drawer can support a maximum of two pairs with each Flash Express feature installed in a unique domain.
•A second PCIe I/O drawer is required to support more than two Flash Express pairs.
•One Flash Express pair is installed in the front slots, 1 and 14. The other pair is installed in the rear slots, 25 and 33.
•Flash Express slot positions are reserved and used only when there are no spare slots available.
•The Flash Express feature has no CHPID assigned. A Flash Express feature has a PCHID assigned to it according to its physical location in the drawer.
•There is no need to define a CHPID for the Flash Express feature in the configuration definition (HCD) or input/output configuration program (IOCP). Take care to avoid the use of Flash Express-associated PCHIDs by another device in the HCD or IOCP definitions.
•Flash Express subchannels are predefined and allocated from the 250 addresses that are reserved in subchannel set 0.
•Flash Express is accessed by using the Z Extended Asynchronous Data Mover (EADM) function. Access to Flash Express is initiated with a Start Subchannel instruction.
•Data is encrypted on the Flash Express adapter with AES key encryption. Encryption keys are stored on smart cards that are plugged into the server’s Support Element. Removing the smart cards renders the data on the Flash Express adapter inaccessible.
•Flash Express features are connected to each other by two external cables to form a RAID 10 mirror for redundancy.
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