Preliminary Information for Creating Stripes and Concatenations

• In DiskSuite terms, stripes and concatenations are "simple metadevices" in that they are composed of slices. Both stripes and concatenations enable you to expand disk storage capacity. They can be used either directly or as the building blocks for mirrors and trans metadevices.

• The system must contain at least three state database replicas before you can create stripes and concatenations. (See Chapter 1, Getting Started.)

• You can use multi-way stripes and concatenations (stripes or concatenations that consist of more than one slice) for any file system except the following:

  • Root (/)

  • swap (You can create multiple, single-slice swap metadevices)

  • /usr

  • /var

  • /opt

  • Any other file system accessed during a Solaris installation or upgrade

• Do not stripe slices that are on the same physical disk. This practice eliminates simultaneous access and reduces performance.

• If possible create metadevices from disks consisting of the same disk geometries. The historical reason is that UFS uses disk blocks based on disk geometries. Today, the issue is centered around performance: a stripe composed of disks with different geometries will only be as fast as its slowest disk.

• When possible, distribute the slices of a stripe or concatenation across different controllers and busses. Using stripes that are each on different controllers increases the number of simultaneous reads and writes that can be performed.

• Do not create a striped metadevice from an existing file system or data. Doing so will destroy data. Instead, use a concatenation. (You can create a striped metadevice from existing data, but you must dump and restore the data to the metadevice.)

• Avoid striping slices with different sizes; this wastes disk space. If necessary, you can assign the unused portion to another slice. The slice must be repartitioned (using format(1M), fmthard(1M), or Storage Manager) to assign the unused disk space to another available slice name.

Because DiskSuite Tool uses the Concat/Stripe object to represent both concatenated metadevices and striped metadevices, the only way to distinguish them by a glance is to study the pattern of rectangles in the Concat/Stripe object.