Planning Your Storage Structure - IBM System Storage DS3500 Introduction And Implementation Manual

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setting through the DS3500 storage management software only. There are no switches on the
EXP3500 or EXP810 chassis to manually set the enclosure ID.
Figure 3-13 Enclosure ID LEDs for EXP3500
Enclosure guidelines
The base controller unit and each expansion enclosure has an ID number associated with it.
The ID allows each enclosure to be identified properly to the base controller unit.
Because the base and all enclosures are connected by Fibre Channel loop, it is necessary for
each ID address to be distinct and unique for I/O to flow properly. An ID address is composed
of two digits: a tens digit (x10) and a ones digit (x1). Enclosure IDs are typically between the
values of x00 and x77.
The EXP3500 is automatically assigned enclosure IDs.
Because the storage system follows a specific address assignment scheme for the drives,
you have to observe a few guidelines when assigning enclosure IDs to expansion units if you
were to assign these manually. Failure to adhere to these guidelines can cause issues with
I/O error recovery, and make the troubleshooting of certain drive communication issues more
difficult:
Whenever possible, maintain an even number of expansion units on the DS3500 Storage
System and configure it for enclosure loss protection. Add EXP expansion units in pairs
and (ideally) for the DS3500 Storage System in groups of four.
Add drives into an expansion enclosure in pairs.

3.3 Planning your storage structure

It is important to configure a storage system in accordance to the needs of the user workload.
An important question and primary concern for most users or storage administrators is how to
configure the storage subsystem to achieve the best performance. There is no simple answer
to fit all cases, and no single guideline for storage performance optimization that is valid in
every environment and for every particular situation. In this section we provide a general (and
less detailed) performance discussion.
Also, in this section, we discuss the use of RAID protection, and review other aspects of the
system configuration that can help optimize the storage capacity and resilience of the system.
In particular, we review array configuration, and enclosure loss protection.
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IBM System Storage DS3500: Introduction and Implementation Guide
Draft Document for Review March 28, 2011 12:24 pm