HP P2000 HP P2000 G3 MSA System SMU Reference Guide - Page 21

Related topics, About spares - g3 msa best practices

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solution. Alternatively, if the host accesses were 128 KB, then each host read would have to access two disks in the vdisk. For random patterns, that ties up twice as many disks. When you create a vdisk you can also create volumes within it. A volume is a logical subdivision of a vdisk, and can be mapped to controller host ports for access by hosts. The storage system presents only volumes, not vdisks, to hosts. You can create vdisks with or without volumes by using the Provisioning Wizard, or you can create vdisks manually. Best practices for creating vdisks include: • To maximize capacity, use disks of similar size. • For greatest reliability, use disks of the same size and rotational speed. • For storage configurations using many disks, create a few vdisks each containing many disks instead of many vdisks each containing a few disks. • To maximize capacity and disk usage (but not performance), you can create vdisks larger than 2 TB and divide them into multiple volumes each having a capacity of 2 TB or less. This increases the usable capacity of storage configurations by reducing the total number of parity disks required when using parity-protected RAID levels. This differs from using a volume larger than 2 TB, which requires specific support by the host operating system, I/O adapter, and application. • For maximum use of a dual-controller system's resources, each controller should own a similar number of vdisks. • Set the chunk size to match the transfer block size of the host application. Related topics • About RAID levels on page 30 • About spares on page 21 • About volumes on page 22 • Vdisk topics in Provisioning the system on page 57 • Configuring a vdisk on page 53 • Verifying a vdisk on page 84 • Scrubbing a vdisk on page 84 • Viewing information about a vdisk (page 92), all vdisks (page 91), or the system (page 89) • Removing a vdisk from quarantine on page 85 About spares A controller automatically reconstructs a redundant (fault-tolerant) vdisk (RAID 1, 3, 5, 6, 10, 50) when one or more of its disks fails and a compatible spare disk is available. A compatible disk has enough capacity to replace the failed disk and is the same type (SAS or SATA). There are three types of spares: • Dedicated spare. Reserved for use by a specific vdisk to replace a failed disk. Most secure way to provide spares for vdisks but expensive to reserve a spare for each vdisk. • Global spare. Reserved for use by any redundant vdisk to replace a failed disk. • Dynamic spare. An available compatible disk that is automatically assigned to replace a failed disk in a redundant vdisk. When a disk fails, the system looks for a dedicated spare first. If it does not find a dedicated spare, it looks for a global spare. If it does not find a compatible global spare and the dynamic spares option is enabled, it takes any available compatible disk. If no compatible disk is available, reconstruction cannot start. A best practice is to designate spares for use if disks fail. Dedicating spares to vdisks is the most secure method, but it is also expensive to reserve spares for each vdisk. Alternatively, you can enable dynamic spares or assign global spares. HP P2000 G3 MSA System SMU Reference Guide 21

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HP P2000 G3 MSA System SMU Reference Guide
21
solution. Alternatively, if the host accesses were 128 KB, then each host read would have to access two
disks in the vdisk. For random patterns, that ties up twice as many disks.
When you create a vdisk you can also create volumes within it. A volume is a logical subdivision of a
vdisk, and can be mapped to controller host ports for access by hosts. The storage system presents only
volumes, not vdisks, to hosts.
You can create vdisks with or without volumes by using the Provisioning Wizard, or you can create vdisks
manually.
Best practices for creating vdisks include:
•
To maximize capacity, use disks of similar size.
•
For greatest reliability, use disks of the same size and rotational speed.
•
For storage configurations using many disks, create a few vdisks each containing many disks instead of
many vdisks each containing a few disks.
•
To maximize capacity and disk usage (but not performance), you can create vdisks larger than 2 TB
and divide them into multiple volumes each having a capacity of 2 TB or less. This increases the usable
capacity of storage configurations by reducing the total number of parity disks required when using
parity-protected RAID levels. This differs from using a
volume
larger than 2 TB, which requires specific
support by the host operating system, I/O adapter, and application.
•
For maximum use of a dual-controller system’s resources, each controller should own a similar number
of vdisks.
•
Set the chunk size to match the transfer block size of the host application.
Related topics
•
About RAID levels
on page 30
•
About spares
on page 21
•
About volumes
on page 22
•
Vdisk topics in
Provisioning the system
on page 57
•
Configuring a vdisk
on page 53
•
Verifying a vdisk
on page 84
•
Scrubbing a vdisk
on page 84
•
Viewing information about a vdisk (
page 92
), all vdisks (
page 91
), or the system (
page 89
)
•
Removing a vdisk from quarantine
on page 85
About spares
A controller automatically reconstructs a redundant (fault-tolerant) vdisk (RAID 1, 3, 5, 6, 10, 50) when one
or more of its disks fails and a compatible spare disk is available. A compatible disk has enough capacity
to replace the failed disk and is the same type (SAS or SATA).
There are three types of spares:
•
Dedicated spare
. Reserved for use by a specific vdisk to replace a failed disk. Most secure way to
provide spares for vdisks but expensive to reserve a spare for each vdisk.
•
Global spare
. Reserved for use by any redundant vdisk to replace a failed disk.
•
Dynamic spare
. An available compatible disk that is automatically assigned to replace a failed disk in
a redundant vdisk.
When a disk fails, the system looks for a dedicated spare first. If it does not find a dedicated spare, it looks
for a global spare. If it does not find a compatible global spare and the dynamic spares option is enabled,
it takes any available compatible disk. If no compatible disk is available, reconstruction cannot start.
A best practice is to designate spares for use if disks fail. Dedicating spares to vdisks is the most secure
method, but it is also expensive to reserve spares for each vdisk. Alternatively, you can enable dynamic
spares or assign global spares.