HP P2000 HP P2000 G3 MSA System SMU Reference Guide - Page 26

About managing remote systems, Related topics, About the Snapshot feature

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About managing remote systems You can add a management object to obtain information from a remote storage system. This allows a local system to track remote systems by their network-port IP addresses and cache their login credentials - the user name and password for a manage-level user on that system. The IP address can then be used in commands that need to interact with the remote system. After a remote system has been added, you can check the connectivity of host ports in the local system to host ports in that remote system. A port in the local system can only link to ports with the same host interface, such as Fibre Channel (FC), in a remote system. Communication between local and remote systems is an essential part of the remote replication feature. Related topics • Adding a remote system on page 52 • Deleting remote systems on page 52 • Viewing information about a remote system on page 105 • Checking links to a remote system on page 87 • About the Remote Snap replication feature on page 107 About the Snapshot feature Snapshot is a licensed feature that provides data protection by enabling you to create and save snapshots of a volume. Each snapshot preserves the source volume's data state at the point in time when the snapshot was created. Snapshots can be created manually or by using the task scheduler. When the first snapshot is taken of a standard volume, the system automatically converts the volume into a master volume and reserves additional space for snapshot data. This reserved space, called a snap pool, stores pointers to the source volume's data. Each master volume has its own snap pool. The system treats a snapshot like any other volume; the snapshot can be mapped to hosts with read-only access, read-write access, or no access, depending on the snapshot's purpose. Any additional unique data written to a snapshot is also stored in the snap pool. The following figure shows how the data state of a master volume is preserved in the snap pool by two snapshots taken at different points in time. The dotted line used for the snapshot borders indicates that snapshots are logical volumes, not physical volumes as are master volumes and snap pools. MasterVolume-1 Snapshot-1 (Monday) Snap Pool-1 Snapshot-2 (Tuesday) Figure 1 Relationship between a master volume and its snapshots and snap pool The snapshot feature uses the single copy-on-write method to capture only data that has changed. That is, if a block is to be overwritten on the master volume, and a snapshot depends on the existing data in the block being overwritten, the data is copied from the master volume to the snap pool before the data is changed. All snapshots that depend on the older data are able to access it from the same location in the snap pool; this reduces the impact of snapshots when writing to a master volume. In addition, only a single copy-on-write operation is performed on the master volume. 26 Getting started

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26
Getting started
About managing remote systems
You can add a management object to obtain information from a remote storage system. This allows a local
system to track remote systems by their network-port IP addresses and cache their login credentials — the
user name and password for a manage-level user on that system. The IP address can then be used in
commands that need to interact with the remote system.
After a remote system has been added, you can check the connectivity of host ports in the local system to
host ports in that remote system. A port in the local system can only link to ports with the same host
interface, such as Fibre Channel (FC), in a remote system.
Communication between local and remote systems is an essential part of the remote replication feature.
Related topics
•
Adding a remote system
on page 52
•
Deleting remote systems
on page 52
•
Viewing information about a remote system
on page 105
•
Checking links to a remote system
on page 87
•
About the Remote Snap replication feature
on page 107
About the Snapshot feature
Snapshot is a licensed feature that provides data protection by enabling you to create and save snapshots
of a volume. Each snapshot preserves the source volume’s data state at the point in time when the snapshot
was created. Snapshots can be created manually or by using the task scheduler.
When the first snapshot is taken of a standard volume, the system automatically converts the volume into a
master volume
and reserves additional space for snapshot data. This reserved space, called a
snap pool
,
stores pointers to the source volume’s data. Each master volume has its own snap pool. The system treats a
snapshot like any other volume; the snapshot can be mapped to hosts with read-only access, read-write
access, or no access, depending on the snapshot’s purpose. Any additional unique data written to a
snapshot is also stored in the snap pool.
The following figure shows how the data state of a master volume is preserved in the snap pool by two
snapshots taken at different points in time. The dotted line used for the snapshot borders indicates that
snapshots are logical volumes, not physical volumes as are master volumes and snap pools.
Figure 1
Relationship between a master volume and its snapshots and snap pool
The snapshot feature uses the single copy-on-write method to capture only data that has changed. That is,
if a block is to be overwritten on the master volume, and a snapshot depends on the existing data in the
block being overwritten, the data is copied from the master volume to the snap pool before the data is
changed. All snapshots that depend on the older data are able to access it from the same location in the
snap pool; this reduces the impact of snapshots when writing to a master volume. In addition, only a single
copy-on-write operation is performed on the master volume.
MasterVolume-1
Snap Pool-1
Snapshot-1
Snapshot-2
(Monday)
(Tuesday)