MSA 2040 SMU Reference Guide

22 Getting started
• No-mirror. In this mode each controller stops mirroring its cache metadata to the partner controller. This improves
write I/O response time but at the risk of losing data during a failover. ULP behavior is not affected, with the
exception that during failover any write data in cache will be lost.
• Atomic write. Not supported.
Related topics
• "Changing a volume’s cache settings" (page 58)
• "Changing system cache settings" (page 53)
• "Viewing information about a volume" (page 106)
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 user with the Manage role 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" (page 56)
• "Deleting remote systems" (page 56)
• "Viewing information about a remote system" (page 122)
• "Checking links to a remote system" (page 92)
• "About the Remote Snap replication feature" (page 123)
About the Snapshot feature
Snapshot is a licensed feature that provides data protection by enabling you to create and save snapshots of a
volume. A base of 64 snapshots is included with all 2040 systems without an additional license. 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.