Xsan 1.4.2 or earlier: Configuring for optimal performance

Many factors will impact performance when you copy files to and from Xsan volumes. While the following suggestions are not essential for proper function, they may improve file read and write speeds on an Xsan volume. This document applies to Xsan 1.4.2 or earlier.

This article has been archived and is no longer updated by Apple.

Determining performance

In order to verify that an Xsan volume is operating optimally, reference the latency values that are reported hourly in an Xsan volume’s log. Each Xsan volume’s log can be referenced in Xsan Admin. In Xsan 1.4.2 or earlier, access the log by selecting an Xsan Volume, then selecting the Logs tab. There is a drop down menu that allows you to read each Metadata Controller’s Xsan volume logs.

Alternately, each Xsan volume’s cvlog can be found at the following path on each Metadata Controller: /Library/Filesystems/Xsan/data/[VolumeName]/log/cvlog

...where VolumeName is the name of your Xsan Volume.

Search the Xsan volume logs for strings starting with:

PIO HiPriWr SUMMARY [Metadata Storage Pool] sysavg

...where Metadata Storage Pool is the name of the Storage Pool that your Xsan volume’s metadata is written to. If the sysavg value are less than 500ms, then the Xsan volume is operating optimally. If the sysavg value exceeds 500ms, make sure that the recommendations in this article are properly configured.

Note: In order for accurate HiPriWr values to be reported in the Xsan volume log, it is first necessary to copy data to and from the Xsan volume. An easy way to do so is to use Xsan Tuner. If using Xsan Tuner, be aware of the information in this article.

Suggested actions

  • When creating volumes, configure Metadata and Journal to exist in a pool that's separate from user data. Storage Pool configuration is discussed in the Xsan Administrator's Guide.
  • If an Xserve RAID is used for metadata storage, ensure that the metadata LUN is on its own RAID controller. If another LUN is placed on the same RAID controller, ensure that this LUN is seldom used.
  • Ensure that the network used for Xsan metadata communications is a separate physical network from the network used for network service communications such as AFP, DNS, Directory Services, and so forth, as described in Xsan documentation:
    1. Ensure that the metadata controllers (MDCs) are set to connect to the Xsan network using the interface that is reserved for metadata communications and not the network interface used for network service communications such as AFP, DNS, Directory Services, etc.

      In Xsan 1.4.2 or earlier, this setting can be verified in Xsan Admin (Setup > Computers). Select each metadata controller (MDC) and click Edit.

    2. In your Port Configurations list, ensure that the network interface used for network service communications such as AFP, DNS, Directory Services, and so forth, is configured with a higher priority than the network interface used for Xsan metadata communications (for instructions, see the "Adjusting port priority" section of "Using network locations in Mac OS X").
    3. Each Xsan unit's network interface used for Xsan metadata communications should be communicating at 1000baseT. It is recommended the metadata communication's interface be configured such that ethernet settings in Network System Preferences > Ethernet settings are configured Automatically. The Ethernet switch should then be configured to allow communications speed as 1000baseT, and duplex settings as Full Duplex, flow-control. To verify that the switch is correctly configured, on each Xsan unit, open Apple System Profiler, select Network, then select the network interface used for Xsan metadata communications. Verify that the interface Media Options are reported as "Full Duplex, flow-control" and Media Subtype is "1000baseT".
  • Ensure that the MDCs are dedicated to Xsan. MDCs perform much better if they are not configured to run services such as AFP, NFS, and so on.
  • Make sure the clocks on all clients are synchronized by selecting a Network Time Server in Date & Time preferences.
  • Attempt to limit the amount of files in any given directory. Apple has not set a limit for the amount of files in a directory, so you may need to test with various configurations.
  • Ensure that minimum RAM requirements are met. Refer to the Xsan Administrator's Guide for specific requirements.
  • Ensure that the Apple Fibre Channel Card is installed in the correct slot for the type of computer that you are using. See the "Xserve RAID FAQ" and article 32480.
  • Ensure that all Fibre Channel Interfaces including the HBA, Fibre Channel Switch, and Fibre storage devices are set to communicate at their maximum potential. Note that connections between 2Gbit devices and 4Gbit devices will operate at a maximum of 2 Gb/s. For more information on fibre hardware interoperability, see this article.
  • Ensure that hosts are connected to the fibre channel switch using all available ports on the PCI HBA.
  • Ensure that on each Xsan node, the Finder's List View options setting "Calculate all Sizes" is disabled. To access this setting, open a Finder window in List view, then from the Finder's View menu choose View Options. Uncheck the option to "Calculate all Sizes".
  • Ensure that Xserve RAIDs are configured for maximum performance. For more information, see this article.
  • RAID performance when usage exceeds 80% capacity:
    - Due to fragmentation and disk geometry, RAID performance may degrade when usage exceeds 80% capacity. Xsan Admin can be configured to send an email to an Administrator when this threshold is exceeded.
    - In Xsan 1.4.2 or earlier, notifications are configured in the Setup panel in Xsan Admin. Select Notifications and check the option to notify if free space falls below 20% of available space.
  • The Volume should be configured to use an allocation strategy that offers best performance. The Roundrobin allocation writes to each available storage pool in succession. Available storage pools are those storage pools that either belong to the affinity to which the data is being written, or if not being written to an affinity, to all pools that are not an affinity-only pool. If a Storage Pool’s bandwidth has been expanded, ensure that snfsdefraghas been run in accordance with the steps described in this article.
    Using the Fill allocation strategy will result in permanently writing to a single storage pool, thus decreasing performance.
    Using the Balance allocation strategy may result in temporarily writing to a less than all available storage pools, thus decreasing performance. Balance, however, will ensure that each Storage pool has an equal amount of data.
  • Ensure that each Xsan client and MDC can resolve their Network Services interface to a Fully Qualified Domain Name.
  • Choose a proper Block Allocation Size and stripe breadth for your volumes. Typically, a Block Allocation Size of 16KB and a Stripe breadth of 64 Blocks will yield the best performance. It is suggested that you benchmark different combinations of these values and then use the combination that yields maximum throughput.
  • Make sure Spotlight indexing is disabled. Spotlight searches of Xsan Volumes are not supported and spotlight indexing of Xsan volumes is disabled by default, but it is possible to enable Spotlight indexing of Xsan volumes. To ensure that spotlight indexing is not enabled for an Xsan volume use the mdutil binary. Execute the following Terminal command to ensure that spotlight indexing is disabled for your Xsan volume:

    sudo mdutil -i off/Volumes/[YourXsanVolume]


Upgrade notes

  1. If you have migrated your volumes from Xsan 1.0.x to Xsan 1.1, you need to manually edit your volume configuration files to provide better performance and stability.
  2. If you've upgraded from a previous version of Xsan to version 1.2, you may need to modify your volume's Journal Size (learn more).
Important: Information about products not manufactured by Apple is provided for information purposes only and does not constitute Apple’s recommendation or endorsement. Please contact the vendor for additional information.
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