User Guide

Chapter 2 Planning a Storage Area Network 29
How Should Users See Available Storage?
If you want the users working on a particular project to see a volume dedicated to their
work, create a separate volume for each project. If it’s acceptable for a user to see a
folder for his or her work on a volume with other peoples’ folders, you can create a
single volume and organize it into project folders.
Workflow Considerations
How much file sharing is required by your users’ workflow? If, for example, different
users or groups work on the same files, either simultaneously or in sequence, it makes
sense to store those files on a single volume to avoid having to maintain or hand off
copies. Xsan uses file locking to manage shared access to a single copy of the files.
Performance Considerations
If your SAN supports an application (such as high resolution video capture and
playback) that requires the fastest possible sustained data transfers, design your SAN
with these performance considerations in mind:
 Set up the LUNs (RAID arrays) using a RAID scheme that offers high performance. See
“Choosing RAID Schemes for LUNs” on page 30.
 Assign your fastest LUNs to an affinity tag for the application. Assign slower LUNs to
an affinity tag for less demanding applications.
 To increase parallelism, spread LUNs across different RAID controllers. Xsan then
stripes data across the LUNs and benefits from simultaneous transfers through two
RAID controllers.
 To increase parallelism for an affinity tag assigned to relatively small LUNs (the size of
one or a few drive modules), create a slice of similar size across all the drives on a
RAID controller instead of creating the LUNs from just one or two drive modules.
 Spread file transfers across as many drives and RAID controllers as possible.
Try creating slices across the drives in RAID systems, and then assign these slices to
the same affinity tag.
 To increase throughput, connect both ports on client Fibre Channel cards to the
fabric.
 Store file system metadata and journal data on a separate storage pool from user
data, and make sure the metadata LUNs are not on the same RAID controller as any
user data LUNs.
 Use a second Ethernet network (including a second Ethernet port in each SAN
computer) for the SAN metadata, or at least use a router to isolate the Ethernet
network used by the SAN from a company intranet or the Internet.
 If your SAN uses directory services, mail services, or other services on a separate
server, connect SAN computers to that server on an Ethernet network separate from
the SAN metadata network.