Xserve RAID 1.5 and later: Configuring for optimal performance

The Apple Xserve RAID 1.5 Update has features that allow you to choose between increasing your Xserve RAID’s stability versus increasing the Xserve RAID's performance. Depending on how you intend to use your Xserve RAID, you will want to choose the options that correspond to increased stability or increased performance.

To take advantage of these new options, you will need to use RAID Admin 1.5 in conjunction with RAID Firmware version firmware-1.5-1.50.xfb.

This article has been archived and is no longer updated by Apple.

RAID Array Configuration

For maximum performance, configure the RAID to be fully populated with seven drives on each side (make one a hot spare if that's your priority) and configure it to have 512 MB RAM. Configure both sides of the Xserve RAID to be RAID Level 5 (Alternately, Xsan metadata LUNs are traditionally RAID1s composed of two drives.). Note that while the RAID set is being constructed, performance is degraded. Depending on the size of the RAID set, construction can take up to 40 hours.

Xserve RAID Fibre Channel Settings

If directly connecting an Xserve RAID to an Apple Fibre Card, the Xserve RAID's topology settings should be set to Point-to-Point.
If connecting an Xserve RAID to a Fibre Channel switch or hub, the Xserve RAID's topology setting should be set to Automatic.

To access these settings:

  1. Select the appropriate RAID in RAID Admin.
  2. Click the Settings button.
  3. Authenticate when prompted.
  4. Select the Fibre Channel tab.
  5. Set the Topology setting. Select either Point to Point or Automatic, based upon the required connection type.

Xserve RAID Performance Settings

Each Xserve RAID Controller has settings that improve performance.

To access these settings:

  1. Select the appropriate RAID in RAID Admin.
  2. Click the Settings button.
  3. Authenticate when prompted.
  4. Select the Performance tab.

Setting 1: Use Controller Write Cache

For maximum performance, select the option to Enable Write caches.

Warning: If you do this, be sure to have an Uninterruptible Power Supply (UPS) system to prevent a data loss scenario. Please review this article for more information.

Setting 2: Allow Host Cache Flushing

If using the Xserve RAID in an Xsan volume: Deselect this option.

RAID Admin 1.5 introduces a new feature that allows the user to control host cache flushing behavior. If your Xserve RAID is used as storage space for video applications, such as Final Cut Pro, you may wish to deselect  the option Allow Host Cache Flushing in order to sustain the bandwidth and low latency for real-time video capture. Likewise, if the Xserve RAID is used for file storage for File Services such as AFP, you may wish to deselect the option Allow Host Cache Flushing. Whenever host cache flushing is turned off, you should connect your RAID to an Uninterruptible Power Supply (UPS) to guard against data loss in the event of a power loss. When video capture is complete, select the option Allow Host Cache Flushing again in order to optimize reliability.

Setting 3: Use Drive Write Cache

For maximum performance, select the option Apple Drive Module (ADM) Drive Cache.

Setting 4: Use Steady Streaming Mode

For maximum performance, deselect this option.

This performance feature can improve short slowdowns in data delivery, but is estimated to reduce overall data delivery bandwidth by as much as 20%. It might be useful in a situation where the RAID appears to be having performance issues reading a particular section of media, but there is not enough time to run the Background Array Conditioning utility.

Setting 5: Read Prefetch

For maximum performance, set the Read Prefetch to 8 stripes (512 KB per disk).

Please refer to the picture below that displays the correct settings:

This is a new utility designed to improve RAID performance and data integrity. This function can be run in the background during times of low data demand (such as rendering, reading email, downloading media) or whenever the Xserve RAID is not in use. Running the Background Array Conditioning utility can be especially useful either just prior to or after making large captures or mastering to tape. The process takes many hours, but can be paused or stopped as needed. For detailed information about Background Array Conditioning, see this article.

Note: Installing the Xserve RAID Admin Tools 1.5 update firmware bundle (firmware-1.5-1.50f.xfb) disables the Xserve RAID Driver 1.0 software settings on the client computers. To regain the host cache flushing behavior, you must select Allow Host Cache Flushing in RAID Admin 1.5.

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