Chunklets; Overview; Physical Disk Chunklets; Spare Chunklets - HP 3PAR StoreServ 7200 2-node Manual

6 Chunklets

Overview

Physical disks are divided into chunklets. When a physical disk is admitted to the system it is divided
into chunklets that become available to the system. Some chunklets are used by logical disks and
other chunklets are designated as spares to hold relocated data during a disk failure or during
maintenance procedures.
Creating, moving, and removing chunklets and spares can only be performed with the HP 3PAR
Command Line Interface (CLI). Refer to the HP 3PAR Command Line Interface Administrator's
Manual for instructions on how to perform these tasks.
Viewing chunklets and spares can be performed with both the HP 3PAR Command Line Interface
(CLI) and the HP 3PAR Management Console. Refer to the HP 3PAR Command Line Interface
Administrator's Manual and the HP 3PAR Management Console Online Help for instructions on
how to perform this task.

Physical Disk Chunklets

Physical disks are divided into chunklets. Each chunklet occupies contiguous space on a physical
disk.
Space on a physical disk is allocated as follows:
On F-Class and T-Class systems all chunklets are 256 MB. On StoreServ 10000 and StoreServ
7000 systems all chunklets are 1 GB.
256 MB of data is reserved for the table of contents (TOC), which contains the internal
description of the system. The TOCs on all physical disks in the system contain the same
information.
4 MB are reserved for diagnostic use, 2 MB beginning after the TOC and 2 MB from the end
of the disk logical block address.
One or more chunklets are allocated as spares. These spare chunklets are used to hold
relocated data during disk failures and during maintenance procedures. Spares are created
during installation and setup. Any chunklet can be reserved as a spare, but the system setup
script selects those chunklets as close to the end of the physical disk's logical block space as
possible.
The remainder of the disk can be used for logical disks.

Spare Chunklets

Some chunklets are identified as spares when the system is first set up at installation. Data from
other chunklets is moved or reconstructed onto these spare chunklets in response to a chunklet or
disk failure or when a drive magazine needs to be serviced. This initial spare storage totals the
amount of storage in a single drive magazine, using the largest size physical disks.
How spare chunklets work:
When a connection is lost to a physical disk or a physical disk fails, all future writes to the
disk are automatically written to a logging logical disk until the physical disk comes back
online or until the time limit for logging is reached. Logging disk space is allocated when the
system is set up. This does not apply to RAID 0 chunklets which have no fault-tolerance.
If the time limit for logging is reached, or if the logging logical disk becomes full, the relocation
of chunklets on the physical disk to free chunklets designated as spares starts automatically.
Free chunklets are any chunklets that are not already allocated for use by logical disks.
32 Chunklets