HP 3PAR StoreServ 7400 2-node HP 3PAR StoreServ Storage Concepts Guide (OS 3.1 - Page 8

Physical Disks, Chunklets, Common Provisioning Groups, Virtual Volumes

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Physical Disks A physical disk is a hard drive mounted on a drive magazine located in an HP 3PAR storage system drive cage. For more information about physical disks and the HP 3PAR storage system hardware platforms, see "HP 3PAR Storage System Hardware" (page 61). Chunklets Physical disks are divided into chunklets. Each chunklet occupies contiguous space on a physical disk. On F-Class and T-Class systems all chunklets are 256 MB. On 10000 and 7000 systems all chunklets are 1 GB. Chunklets are automatically created by the HP 3PAR Operating System and they are used to create logical disks. A chunklet is assigned to only one logical disk. For more information about chunklets, see "Chunklets" (page 32). Logical Disks A logical disk is a collection of physical disk chunklets arranged as rows of RAID sets. Each RAID set is made up of chunklets from different physical disks. Logical disks are pooled together in Common Provisioning Groups (CPGs) which allocate space to virtual volumes. The underlying logical disks are automatically created by the HP 3PAR OS when you create CPGs. The RAID type, space allocation, growth increments and other logical disk parameters can be set when you create a CPG or modified later. HP 3PAR storage systems support the following RAID types: • RAID 0 • RAID 10 (RAID 1) • RAID 50 (RAID 5) • RAID MP (Multi-Parity) or RAID 6 For a detailed discussion of logical disks and RAID types, see "Logical Disks" (page 34). Common Provisioning Groups A CPG is a virtual pool of logical disks that allocates space to virtual volumes on demand. A CPG allows virtual volumes to share the CPG resources. You can create fully provisioned virtual volumes (FPVVs) and thinly-provisioned virtual volumes (TPVVs) that draw space from a CPG logical disk pool. For more information about CPGs, see "Common Provisioning Groups" (page 39). Virtual Volumes Virtual volumes draw their resources from CPGs, and volumes are exported as logical unit numbers (LUNs) to hosts. Virtual volumes are the only data layers visible to the hosts. You can create physical copies or virtual copy snapshots of virtual volumes that remain available if the original base volume becomes unavailable. Before creating virtual volumes, you must first create CPGs to allocate space to the virtual volumes. For more information about virtual volumes, see "Virtual Volumes" (page 42). Fully-provisioned Virtual Volumes An FPVV is a volume that uses logical disks that belong to a CPG. Unlike TPVVs, FPVVs have a set amount of user space that is allocated for user data. The FPVV size is fixed, and the size limit is 16 TB. For more information about fully provisioned virtual volumes, "Fully-Provisioned Virtual Volumes" (page 43). Thinly-provisioned Virtual Volumes A TPVV is a volume that uses logical disks that belong to a CPG. TPVVs associated with the same CPG draw space from the logical disk pool as needed, allocating space on demand in small increments for each controller node. As the volumes that draw space from the CPG require additional storage, the HP 3PAR OS automatically creates additional logical disks and adds them to the pool until the CPG reaches the user-defined growth limit which restricts the CPG maximum size. The 8 Overview

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Physical Disks
A physical disk is a hard drive mounted on a drive magazine located in an HP 3PAR storage
system drive cage. For more information about physical disks and the HP 3PAR storage system
hardware platforms, see
“HP 3PAR Storage System Hardware” (page 61)
.
Chunklets
Physical disks are divided into chunklets. Each chunklet occupies contiguous space on a physical
disk. On F-Class and T-Class systems all chunklets are 256 MB. On 10000 and 7000 systems all
chunklets are 1 GB. Chunklets are automatically created by the HP 3PAR Operating System and
they are used to create logical disks. A chunklet is assigned to only one logical disk. For more
information about chunklets, see
“Chunklets” (page 32)
.
Logical Disks
A logical disk is a collection of physical disk chunklets arranged as rows of RAID sets. Each RAID
set is made up of chunklets from different physical disks. Logical disks are pooled together in
Common Provisioning Groups (CPGs) which allocate space to virtual volumes. The underlying
logical disks are automatically created by the HP 3PAR OS when you create CPGs. The RAID type,
space allocation, growth increments and other logical disk parameters can be set when you create
a CPG or modified later. HP 3PAR storage systems support the following RAID types:
•
RAID 0
•
RAID 10 (RAID 1)
•
RAID 50 (RAID 5)
•
RAID MP (Multi-Parity) or RAID 6
For a detailed discussion of logical disks and RAID types, see
“Logical Disks” (page 34)
.
Common Provisioning Groups
A CPG is a virtual pool of logical disks that allocates space to virtual volumes on demand. A CPG
allows virtual volumes to share the CPG resources. You can create fully provisioned virtual volumes
(FPVVs) and thinly-provisioned virtual volumes (TPVVs) that draw space from a CPG logical disk
pool. For more information about CPGs, see
“Common Provisioning Groups” (page 39)
.
Virtual Volumes
Virtual volumes draw their resources from CPGs, and volumes are exported as logical unit numbers
(LUNs) to hosts. Virtual volumes are the only data layers visible to the hosts. You can create physical
copies or virtual copy snapshots of virtual volumes that remain available if the original base volume
becomes unavailable. Before creating virtual volumes, you must first create CPGs to allocate space
to the virtual volumes. For more information about virtual volumes, see
“Virtual Volumes” (page 42)
.
Fully-provisioned Virtual Volumes
An FPVV is a volume that uses logical disks that belong to a CPG. Unlike TPVVs, FPVVs have a set
amount of user space that is allocated for user data. The FPVV size is fixed, and the size limit is
16 TB. For more information about fully provisioned virtual volumes,
“Fully-Provisioned Virtual
Volumes” (page 43)
.
Thinly-provisioned Virtual Volumes
A TPVV is a volume that uses logical disks that belong to a CPG. TPVVs associated with the same
CPG draw space from the logical disk pool as needed, allocating space on demand in small
increments for each controller node. As the volumes that draw space from the CPG require additional
storage, the HP 3PAR OS automatically creates additional logical disks and adds them to the pool
until the CPG reaches the user-defined growth limit which restricts the CPG maximum size. The
8
Overview