EMC: Logical Architecture

Title:EMC: Logical Architecture
Author:Douglas O’Leary <dkoleary@olearycomputers.com>
Description:Logical architecture of EMC Symmetrix
Date created:06/2001
Date updated:07/2005
Disclaimer:Standard: Use the information that follows at your own risk. If you screw up a system, don’t blame it on me...

The diagram below depicts the Symmetrix family logical architecture. This is the one that you’ll have to understand; the physical side, for the most part, can be left to EMC.


Every symmetrix has director slots labeled 1-16. Smaller Symmetrixes will have the middle numbers missing; however, there will be a 1 and there will be a 16.

On the left side of the diagram, you see two boards labled SA05 and FA07. These are the host adapters into which you plug your hosts. The FA/SA describes what kind of interface the board supports. In this case, SCSI (SA) and Fibre (FA). The number following the FA/SA is the director/slot number.

The other side of the diagram shows the disk adapters (DA). These connect the physical disks. The physical disks are usually split into chunks called hypervolume extensions and numbered hexadecimally.

The hypervolume extensions are then logically mapped to the various host adapters through the bin file. On SCSI host adapters, the hypervolume is given a target and lun number that the host will see. Fibre adapters, on the other hand, only have the lun number. Target numbers are assigned in the order in which the controller sees them through the fibre channel zoning. More information on that in a different page.

Both host and disk adapters have two processors, A & B. Most adapters have four ports (fibre being the exception - currently only has two). Two adapters each, labeled 0 & 1, are connected to each proccessor. The ports on disk adapters are labeld C & D.

In between host and disk adapters, we have the mother of all caches. The cache, for the most part, can be thought of as a black box. Although it’s nice to know that each hypervolume extension has its own chunk of cache and that the Symmetrix uses a mailbox functionality to pass messages; those types of details are irrelevant to the day to day operation of a Symmetrix. Understanding how the disks are addressed on EMC s/w reports, however, is very relevant.

So, we now have enough information to describe the EMC labeling. Using the diagram above, we have four boards: 2 host adapters, and two disk adapters. EMC labels the adapters in the following format:

Adapter type. Most common,
FA, SA, DA (disk adapter)
DA Adapter type. Most common, FA, SA, DA (disk adapter)
05 Director number 09 Director number
B Processor letter A Processor letter
0 Port number D Port number