Striped Metadevice Conventions

• Why would I create a striped metadevice?

  To take advantage of the performance increases that come from accessing data in parallel and to increase capacity. Always use striped metadevices for new file systems or data sets.

  Striping enables multiple controllers to access data at the same time (parallel access). Parallel access can increase I/O throughput because all disks in the metadevice are busy most of the time servicing I/O requests.

  Striping is good for large sequential I/O and for uneven I/O.

• What are the limitations to striping?

  An existing file system cannot be directly converted to a striped metadevice. If you need to place a file system on a striped metadevice, you can back up the file system, create a striped metadevice, then restore the file system to the striped metadevice.

  When creating a stripe, do not use slices of unequal size, as this will result in unused disk space.

• What is an interlace value?

  The size, in Kbytes, Mbytes, or blocks, of the logical data chunks in a striped metadevice. Depending on the application, different interlace values can increase performance for your configuration. The performance increase comes from several disk arms doing I/O. When the I/O request is larger than the interlace size, you may get better performance.

• What is DiskSuite's default interlace value?

  16 Kbytes.

• Can I set the interlace value?

  Yes, when you create a new striped metadevice, using either the command line or DiskSuite Tool. Once you have created the striped metadevice, you cannot change the interlace value.

• Can I set the interlace value on an existing striped metadevice?

  No. (Though you could back up the data on it, delete the striped metadevice, create a new striped metadevice with a new interlace value, and then restore the data.)

RAID5 metadevices also use an interlace value. See "RAID5 Metadevices" for more information.