HP XP Racks - Manual (Page 57)

Particularly, in the following cases of quick format operations, due to the load concentration on a
specific component at the same time, the I/O performance of the host may decrease while
performing of the quick format.
•
In a configuration that satisfies both of these conditions, many quick formats started at the
same time.
◦ The number of modules is one or two.
◦ Configuration of CPEX (Cache Path control adapter and PCI EXpress path switch), DKA
(DisK Adapter), and CHA (CHannel Adapter) are minimum in each module
•
In a configuration that satisfies either one of these conditions, quick formats started.
In the multiple modules configuration, the number of CPEXs, DKAs, and CHAs that are
installed in each module, are extremely unbalanced between modules.
For example, in the multiple modules configuration, one module contains many CPEX,
DKA, and CHA, and other modules contains CPEX, DKA, and CHA of the least number.
◦
◦ In a module, numbers of CPEXs, DKAs, and CHAs that connect to CPEX (Basic) or CPEX
(Option) are extremely unbalanced between CPEX (Basic) and CPEX (Option).
For example, inside of one module, CPEX (Basic) is connected by many DKAs, CHAs, or
other devices. However, CPEX (Option) is connected by DKAs, CHAs, or other devices
of the least number.
For configurations such as those described above, perform the quick format operation on one LDEV
first to confirm that the I/O performance of the host does not decrease. After that, it is strongly
recommended that the number of quick format operations you perform at the same time is increased
one by one.
For configurations other than those described above, it is recommended that no more than eight
quick format operations are started at the same time. After eight or fewer quick formats, it is
recommended that four quick format operations are started in each increment while I/O performance
is monitored on the host.
Quick Format specifications
Description Item
The internal volume must be in blocked status. Preparation for executing the
Quick Format feature
Up to 72 parity groups can concurrently undergo Quick Format. There is no limit on
the number of volumes that can undergo Quick Format. The number of parity groups
that can undergo Quick
Format
While one Quick Format operation is in progress, another Quick Format operation can
be performed. A maximum of 72 parity groups can concurrently undergo Quick Format. Concurrent Quick Format
operations
At the beginning of the Quick Format operation, preliminary processing is performed
to generate management information. If a volume is undergoing preliminary processing, Preliminary processing
the status of the volume is Preparing Quick Format. While preliminary processing is in
progress, hosts cannot perform I/O access to the volume.
If a volume undergoing Quick Format is blocked, the storage system recognizes that
the volume is undergoing Quick Format. After the volume is restored, the status of the
volume changes to Normal (Quick Format). Blocking and restoring of
volumes
If all volumes in one or more parity groups undergoing Quick Format are blocked, the
displayed number of parity groups undergoing Quick Format decreases by the number
of blocked parity groups. However, the number of parity groups that have not undergone
and can undergo Quick Format does not increase. To calculate the number of parity
Formatting LDEVs 57