H.2 Using Flash Express - IBM z13s Technical Manual

For higher resiliency and high availability, Flash Express cards are always installed in pairs. A
maximum of four pairs are supported in a z13s system, providing a maximum of 5.6 TB of
storage. In each Flash Express card, data is stored in a RAID configuration. If an SSD fails,
data is reconstructed dynamically. The cards mirror each other over a pair of cables in a
RAID 10 configuration that combines mirroring and striping RAID capabilities. If either card
fails, the data is available on the other card. Card replacement is concurrent with the client's
operations. In addition, Flash Express supports concurrent firmware upgrades.
The data that is written on the Flash Express cards is always stored encrypted with a volatile
key. The card is only usable on the system with the key that encrypted it. For key
management, both the primary and alternate Support Elements (SEs) have USB smart cards
installed. The smart card contains both a unique key that is personalized for each system and
a small Crypto engine that can run a set of security functions within the card.

H.2 Using Flash Express

Flash Express is designed to improve availability and latency from batch to interactive
processing in z/OS environments, such as start of day. It helps accelerate start of day
processing when there is heavy application activity. Flash Express also helps improve
diagnostic procedures, such as supervisor call (SAN Volume Controller) memory dumps, and
stand-alone memory dumps.
In z/OS, Flash Express memory is accessed by using the new z Systems Extended
Asynchronous Data Mover (EADM) architecture. It is started with a Start subchannel
instruction.
The Flash Express PCIe cards are shareable across logical partitions (LPARs). Flash
Express memory can be assigned to z/OS LPARs, such as the main storage. It is dedicated to
each LPAR. You can dynamically increase the amount of Flash Express memory that is
allocated to an LPAR.
Flash Express is supported by z/OS 1.13 plus PTFs, and z/OS 2.1 for the z/OS paging activity
and SAN Volume Controller memory dumps. Using Flash Express memory, 1 MB large pages
become pageable. It is expected to provide applications with substantial improvement in SAN
Volume Controller memory dump data capture time. Flash Express is expected to provide the
applications with improved resiliency and speed, and make large pages pageable.
Flash Express memory in the CPC is assigned to a coupling facility (CF) partition by using
hardware definition windows the same way that it is assigned to the z/OS partitions.
Flash Express use by the CF provides emergency capacity to handle WebSphere MQ shared
queue buildups during abnormal situations. These situations include where "putters" are
putting to the shared queue, but "getters" are transiently not getting from the shared queue, or
other such transient producer or consumer mismatches on the queue. No new level of
WebSphere MQ is required for this support.
Linux for z Systems (Red Hat Enterprise Linux and SUSE Linux enterprise) can use Flash
Express as temporary storage. Other software subsystems might take advantage of Flash
Express in the future.
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IBM z13s Technical Guide