Apple Xsan 1.4 - Manual (Page 42)

42 Chapter 2 Setting Up a Storage Area Network
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 44.
 Group your fastest LUNs in storage pools reserved for the application. Reserve slower
devices for a volume dedicated to less demanding or supporting applications.
 To increase parallelism, spread LUNs across different Xserve RAID controllers. For
example, instead of creating a single 4-disk LUN on one side of an Xserve RAID, create
two 2-disk LUNs, one on each side, and add these LUNs to a storage pool. Xsan then
stripes data across the two LUNs and benefits from simultaneous transfers through
two controllers.
 To increase parallelism in a relatively small storage pool (the size of one or a few drive
modules), create a slice of similar size across all the drives on a controller instead of
creating the storage pool 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 combine these slices
into a storage pool.
 To increase throughput, connect both ports on client Fibre Channel cards to the
fabric and set the multipathing method for the storage pool to Rotate.
 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.