Apple Xsan 2 (Third Edition) - Manual (Page 26)

Preliminary Planning Questions
As you plan, consider the following questions:
How much storage do you need? Â
How do you want to present available storage to users? Â
What storage organization makes the most sense for user workflow? Â
What levels of performance do users require? Â
How important is high availability? Â
What are your requirements for security? Â
Your answers to the questions above will help you decide the following:
What RAID schemes should you use for your RAID arrays? Â
How many SAN volumes do you need? Â
How should individual volumes be organized? Â
Which preset volume type can you choose for each volume? Â
Which LUNs should be assigned to each affinity tag? Â
Which clients, users, and groups should have access to each volume? Â
Which computers will act as metadata controllers? Â
Do you need standby metadata controllers? Â
Do you need to adjust a volume’s allocation strategy? Â
How should you configure your Ethernet network? Â
Review the considerations and guidelines on the following pages for help creating a
suitable SAN design.
Planning Considerations and Guidelines
The following considerations might help improve your SAN design decisions.
How Much Storage?
Because it’s easy to add storage for user data to an Xsan SAN, you only need to decide
on an adequate starting point. You can add storage later as needed.
However, you can’t expand a storage pool that can only store volume metadata and
journal data, so try to allocate enough space for metadata right from the start. (You
can add an entire storage pool for metadata and journal storage.) For help estimating
your metadata and journal data storage requirements, see “Estimating Metadata and
Journal Data Storage Needs” on page 31.
Note that the number of RAID systems you use affects not only available space but
also SAN performance. See “Performance Considerations” on page 27.
26 Chapter 2 Planning a Storage Area Network