4
4-2
EMCFib re Channel Storage Systems Configuration Planning Guide
Planning LUNs and File Systems with Unshared Direct Storage
Dual SPs and Paths to LUNs
If a storage system has two SPs, there are two routes to its LUNs. If
the server has two adapters and the storage system has two SPs,
Application Transparent Failover (ATF). ATF can automatically
switch to the other path, without disrupting applications, if a device
(such as a host-bus adapter, cable, or SP) fails.
Unshared Direct and Shared-or-Clustered Direct Storage
This section explains the direct (unswitched) options available for
connecting storage systems to servers. As needs change, you may
want to change a configuration. You can do so without changing your
LUN configuration or losing user data.
There are two types of installation:
•Unshared direct with one server is the simplest and least costly;
•Shared-or-clustered direct lets two clustered servers share
storage resources with high availability.

Sample Unshared Direct Installation

Figure4-1 Unshared Direct Installation
EMC1825
Disk IDs
100-109
010-019
Database
RAID 5 Users
RAID 5
Sys
RAID 1
Clients, mail
RAID 5
SP A SP B
Adapter
Adapter
Server
Path 1
Path 2