Administrator Guide

Live Volume ALUA
Asymmetric Logical Unit Access (ALUA) is a set of SCSI concepts and commands that dene path prioritization for SCSI devices. It allows
paths to be described as fast, slow, or down and allows transitions between these states using a common standard. Live Volume ALUA
reports Active/Optimized and Active/Non-optimized ALUA states on the primary and secondary volumes/storage systems, respectively.
Live Volume ALUA Optimization Considerations
Live Volume ALUA is used to control the priority of paths for the Primary and Secondary Live Volume components. By default, volume
mapping is Active/Optimized on the primary volume path and Active/Non-optimized on the secondary volume path. This section provides
information about the design features of Live Volume ALUA.
• ALUA Optimization Wizard – On the Live Volumes tab in the Replications & Live Volumes view, the Live Volume table shows if
existing Live Volumes are ALUA optimized. If non-optimized Live Volumes are available and capable of being ALUA optimized, a message
is displayed in a banner at the top of this view. Clicking the Update to ALUA Optimized button in the banner opens the ALUA
optimization wizard. The wizard provides a guided process to enable ALUA optimization on existing Live Volumes.
• Host MPIO Drivers – Due to the path information memory of Multipath Input Output (MPIO) drivers on various servers, it is necessary
for the system to undergo a service outage (such as server rescans or reboots) for Live Volume ALUA support to be fully enabled.
Because it is a disruptive operation, enabling Live Volume ALUA should be performed during a maintenance window.
• Microsoft Windows Environments – When all paths are reported as non-optimized, MPIO drivers will not round-robin as expected and
data transfer is reduced to a single path causing a delayed failover. Therefore, using non-optimized paths is not recommended in
Microsoft Windows environments and reporting non-optimized path reporting should be disabled. Enable or disable non-optimized path
reporting as follows:
– In the ALUA optimization wizard: Disable non-optimized path reporting by clearing the Report Non-optimized Paths checkbox
(refer to Enable Live Volume ALUA Optimization).
– In the Edit Live Volume Settings dialog box: Enable or disable non-optimized path reporting by clearing or setting the Report Non-
optimized Paths checkbox (refer to Enable or Disable Non-Optimized Path Reporting).
NOTE
: Certain Windows Server 2016 versions can support non-optimized path reporting properly. For more information and
best practice guidelines for conguring MPIO on Microsoft Server 2016, refer to the Dell EMC SC Series Storage and
Microsoft Multipath I/O white paper located on the Dell support site.
• Existing Live Volumes – Live Volume ALUA is not automatically enabled on existing Live Volumes after their primary and secondary
systems are upgraded. Instead, use the ALUA optimization wizard to enable Live Volume ALUA. Refer to Enable Live Volume ALUA
Optimization.
• Restore Points – A Live Volume recreated from a restore point is automatically created with ALUA optimization regardless of whether
the original Live Volume was ALUA optimized. The restore point does not retain the current optimized ALUA information.
• Swapping Roles – If ALUA optimization is enabled, Live Volume will report the correct ALUA states consistent with its primary/
secondary Storage Center state during and at completion of a swap role operation. Swapping roles will not enable ALUA optimization.
• Creating New Live Volumes – If both the primary and secondary Storage Centers support ALUA optimization, then Live Volume ALUA
is automatically enabled when a new Live Volume is created. When you use the ALUA optimization wizard to create new Live Volumes,
the Report Non-optimized Paths feature can be congured during the creation process. Refer to Enable Live Volume ALUA
Optimization.
• Converting Replicated Volumes – If both the primary and secondary Storage Centers support ALUA optimization, then Live Volume
ALUA is automatically enabled when a replicated volume is converted to a Live Volume. After the replication is converted, the Report
Non-optimized Paths feature can be congured using the Edit Live Volume Settings dialog box. Refer to Enable or Disable Non-
Optimized Path Reporting.
• Converting Existing Volumes – If both the primary and secondary Storage Centers support ALUA optimization, then Live Volume
ALUA is automatically enabled when an existing volume is converted to a Live Volume. When you use the ALUA optimization wizard to
convert existing Live Volumes, the Report Non-optimized Paths feature can be congured during the optimization process. Refer to
Enable Live Volume ALUA Optimization.
• Storage Center Alerts – When a system is upgraded to Storage Center 7.3 and it is part of an existing Live Volume, the Storage
Manager displays an alert that says the system supports ALUA optimized Live Volumes. The message instructs you to use the ALUA
optimization wizard to enable the Live Volume ALUA feature on existing Live Volumes.
NOTE
: This alert is displayed after one side of the Live Volume is upgraded. It is necessary to upgrade both sides of the
eligible Live Volume to access the Live Volume ALUA optimization wizard.
562 Storage Center Replications and Live Volumes