Specifications

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With PowerPath, not only are multiple channels used to share the I/O workload, but also the automatic
load balancing capability ensures that they are utilized in the most efficient manner possible.
Multipathing allows for two or more data paths (up to 16 for DAS and up to 32 for Symmetrix) to be
simultaneously used for read/write operations. Performance is thereby enhanced by automatically and
equally dispersing data access across all the available paths. PowerPath’s workload balancing feature
ensures that no one path can become overloaded while others have underutilized bandwidth causing an
I/O bottleneck. When one or more paths become busier than others, PowerPath shifts the I/O traffic
from the busy paths to the others, further enhancing throughput over the already efficient multipathing
feature.
PowerPath’s automatic path failover and dynamic recovery feature permits data access to be
immediately and non-disruptively dispersed to an alternate data path or paths in the event of a failure.
This eliminates the possibility of disrupting an application due to the failure of an adapter, cable, or
channel controller. In the event of a path failover, all outstanding and subsequent I/O requests are
automatically and non-disruptively directed to the alternative path. Mission-critical applications
continue without interruption and the customer business stays online.
PowerPath has increased its functionality by extending Intelligent Path Management to support
failover between the switch and the storage. Instead of losing an active HBA in the event of a path
failure, PowerPath fails over to an alternative channel resulting in the path being restored. Mission-
critical applications continue without interruption, your business remains online, performance is
maximized, and your storage assets are maximized. PowerPath's Auto Detect and Auto Restore
features allow for periodic probing of inactive paths to check for path failures. Once the failure has
been detected and repaired, the path is automatically restored. There is no user intervention required.
PowerPath is particularly beneficial in cluster environments in that it can prevent costly interruptions
to operations. PowerPath’s path failover capability avoids node failover, thus maintaining
uninterrupted application support on the primary node in the event of a single path disconnect.
The migration ATF to PowerPath is available only for DAS4500, DAS4700 and DAS5300
4.7. Access Logix (DAS 4500, DAS 4700 and DAS 4700-2)
Access Logix is an optional feature of the DAS 4500, DAS 4700 and DAS 4700-2, which is managed
exclusively by the Navisphere Manager on NT. The purpose is to control storage allocation when the
array is shared and/or reachable by multiple servers, typically in SAN configurations. Access Logix
enables safe, secure information access.
This feature controls the access of hosts to LUNs within the DAS 4500. LUNs are grouped in storage
groups. For each storage group, one or multiple servers are authorized, and will be able to discover the
LUNs, read and write the data. The other servers will not be able to send any SCSI command to the
LUNs of the storage group. A server can use resources spread across multiple DAS subsystems. In
such a case, the storage administrator must configure the LUN access rule for each individual DAS.