Specifications

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redundancy and continuous availability in the event of repair or replacement to any one Channel
Director. These include ESCON channels, SCSI and Fibre Channels, and Remote Link Directors.
Multi Host Support:
Open systems connect to Symmetrix systems through Ultra SCSI and Fibre Channel interfaces. For a
more detailed list of specific server models and supported operating system versions and interface
technologies check EMC partner’s web site at:
https://powerlink.emc.com/
Host Cluster Support:
Configuring hosts in clusters achieves high availability and high performance. Cluster nodes share
access to Symmetrix systems via fast-wide SCSI, Ultra SCSI, and Fibre Channel interfaces. For more
detailed information on Symmetrix support for clustered environments, check EMC partner’s web site
at:
https://powerlink.emc.com/
5.2.2. Internal Data Flow
Intelligent cache configurations allow Symmetrix systems to transfer data at electronic memory speeds
that are much faster than physical disk speeds. Symmetrix products are based on the principle that the
working set of data at any given time is relatively small when compared to the total system storage
capacity. When this working set of data is in cache, there is a significant improvement in I/O
performance. The performance improvement achieved is dependent on both:
Locality of Reference: If a given piece of data is used, there is a high probability that a nearby
piece of data will be used shortly thereafter,
Data Reuse: If a given piece of data is used, there is a high probability that it will be reused shortly
hereafter.
5.2.3. Disk Drives
Symmetrix systems use advanced technology disk drives and disk controllers to enhance Symmetrix
capabilities. Microprocessors embedded in the controllers of each drive enable capabilities such as
advanced RAID protection to be offloaded from CPUs, disk directors and controllers. This further
enhances the performance of Symmetrix systems and also serves to make them more easily compatible
with a wide array of hardware and software platforms.
5.2.4. Disk Directors
The Disk Directors manage the interface to the physical disk, and are responsible for data movement
between the HDAs and cache. HDAs are connected to Disk Directors through industry-standard SCSI
interfaces with two microprocessors per Disk Director. This connection allows rapid introduction of
the latest disk drive technology into Symmetrix systems.