Apple Xsan 1.x - Manual (Page 13)

Chapter 1 Setup and Tuning Guidelines 13
Configuring the Xsan File System
The following paragraphs summarize information you should consider when using
Xsan Admin to configure your Xsan volumes.
Organizing LUNs, Storage Pools, and Volumes
As you combine LUNs into storage pools and add storage pools to a volume, try to:
 Keep metadata in a storage pool on a separate RAID controller
 Add an even number of LUNs to each storage pool
Separate Metadata From User Data
To prevent user data transactions from interfering with metadata transactions, create a
separate storage pool for metadata and journal data and assign that pool to a separate
LUN and controller.
The recommended metadata LUN consists of only two drives (see “Use RAID 1 for
Metadata LUNs” on page 10). To avoid wasting additional drives in the half of the
Xserve RAID system that contains the metadata LUN, you can do either of the
following:
 Move the spare drives to another system
 Use the drives to create a second LUN where you store files that are seldom accessed
It’s also possible to create separate storage pools for metadata and journal data,
although Xsan Admin only lets you segregate the two together. To create separate
pools for metadata and journal, you must work directly with the configuration file for
the volume.
For more information on working directly with the configuration files, see the
command-line appendix of the Xsan Administrator’s Guide or the
cvfs_config man
page. You can also look at the example configuration files in
/Library/Filesystems/Xsan/Examples
Set Up an Even Number of LUNs
Storage pools consisting of an even number of LUNs outperform pools consisting of an
odd number of LUNs.
Volume and Storage Pool Settings
To determine the best settings for your Xsan volume, you might need to try several
combinations, testing each with the Xsan Tuner application and comparing the results.
Choosing a Volume Block Allocation Size
In general, smaller file system block sizes are best in cases where there are many small,
random reads and writes, as when a volume is used for home directories or general file
sharing. In cases such as these, the default 4 KB block size is best.