RAID-1 and RAID-0 Volume Requirements and Guidelines

When you are working with RAID-1 volumes (mirrors) and RAID-0 volumes (single-slice concatenations), consider the following guidelines.

JumpStart and Live Upgrade Guidelines

The custom JumpStart installation method and Live Upgrade support a subset of the features that are available in the Solaris Volume Manager software. When you create mirrored file systems with these installation programs, consider the guidelines in the following table.

Table 9-1 JumpStart and Live Upgrade Guidelines for Creating Mirrored File Systems

RAID Volume Name Requirements and Guidelines

Observe the following rules when assigning names for volumes:

• Use a naming method that maps the slice number and disk number to volume numbers.

• Volume names must begin with the letter d followed by a number, for example, d0.

• Solaris Volume Manager has 128 default volume names from 0–127. The following list shows some example volume names.

  • Device /dev/md/dsk/d0 – block volume d0

  • Device /dev/md/dsk/d1 – block volume d1

• Use ranges for each particular type of volume. For example, assign numbers 0–20 for RAID-1 volumes, and 21–40 for RAID-0 volumes.

RAID Volume Naming Conventions for Live Upgrade

When you use Live Upgrade to create RAID-1 volumes (mirrors) and RAID-0 volumes (submirrors), you can enable the software to detect and assign volume names, or you can assign the names. If you enable the software to detect the names, the software assigns the first mirror or submirror name that is available.

If you assign mirror names, assign names ending in zero so that the installation can use the names ending in 1 and 2 for submirrors. If you assign numbers incorrectly, the mirror might not be created. For example, if you specify a mirror name with a number that ends in 1 or 2 (d1 or d2), Live Upgrade fails to create the mirror if the mirror name duplicates a submirror's name.

Example 9-1 Live Upgrade: Enable the Software to Detect and Name the Mirror and Submirror

In this example, Live Upgrade assigns the volume names. The RAID-1 volumes d0 and d1 are the only volumes in use. For the mirror d10, Live Upgrade chooses d2 for the submirror for the device c0t0d0s0 and d3 for the submirror for the device c1t0d0s0.

lucreate -n newbe -m /:/dev/md/dsk/d10:mirror,ufs  \
-m /:/dev/dsk/c0t0d0s0:attach -m /:/dev/dsk/c1t0d0s0:attach

Example 9-2 Live Upgrade: Assign Mirror and Submirror Names

In this example, the volume names are assigned in the command. For the mirror d10, d11 is the name for the submirror for the device c0t0d0s0 and d12 is the name for the submirror for the device c1t0d0s0.

lucreate -n newbe -m /:/dev/md/dsk/d10:mirror,ufs \
-m /:/dev/dsk/c0t0d0s0,/dev/md/dsk/d11:attach \
-m /:/dev/dsk/c1t0d0s0,/dev/md/dsk/d12:attach

For detailed information about Solaris Volume Manager naming requirements, see Solaris Volume Manager Administration Guide.

RAID-Volume Naming Conventions for JumpStart

When you use the JumpStart installation method to create RAID-1 volumes (mirrors) and RAID-0 volumes (submirrors), you can enable the software to detect and assign volume names to mirrors, or you can assign the names in the profile.

• If you enable the software to detect the names, the software assigns the first volume number that is available.

• If you assign names in the profile, assign mirror names ending in zero so that the installation can use the names ending in 1 and 2 for submirrors.

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  Note - If you assign numbers incorrectly, the mirror might not be created. For example, if you specify a mirror name with a number that ends in 1 or 2 (d1 or d2), JumpStart fails to create the mirror if the mirror name duplicates a submirror's name.

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Example 9-3 JumpStart: Enable the Software to Detect the Mirror and Submirror Names

In the following profile example, the mirror is assigned the first volume numbers that are available. If the next available mirror ending in zero is d10, then the names d11 and d12 are assigned to the submirrors.

filesys                 mirror c0t0d0s1  / 

Example 9-4 JumpStart: Assigning Mirror and Submirror Names

In the following profile example, the mirror number is assigned in the profile as d30. The submirror names are assigned by the software, based on the mirror number and the first available submirrors. The submirrors are named d31 and d32.

filesys                 mirror:d30 c0t1d0s0 c0t0d0s0  /

For detailed information about Solaris Volume Manager naming requirements, see Solaris Volume Manager Administration Guide.

Guidelines for Selecting Disks and Controllers

When you choose the disks and controllers that you want to use to mirror a file system, consider the following guidelines:

• Use components that are on different controllers to increase the number of simultaneous reads and writes that can be performed.

• Keep the slices of different submirrors on different disks and controllers. Data protection is diminished considerably if slices of two or more submirrors of the same mirror are on the same disk.

• Organize submirrors across separate controllers, because controllers and associated cables tend to fail more often than disks. This practice also improves mirror performance.

• Use the same type of disks and controllers in a single mirror. Particularly in old SCSI storage devices, different models or brands of disk or controller can have widely varying performance. Mixing the different performance levels in a single mirror can cause performance to degrade significantly.

Guidelines for Selecting Slices

When you choose the slices that you want to use to mirror a file system, consider the following guidelines:

• Any file system, including root (/), swap, and /usr, can use a mirror. Any application, such as a database, also can use a mirror.

• Make sure that your submirror slices are of equal size. Submirrors of different sizes result in unused disk space.

• If you have a mirrored file system in which the first submirror attached does not start on cylinder 0, all additional submirrors you attach also must not start on cylinder 0. If you attempt to attach a submirror starting on cylinder 0 to a mirror in which the original submirror does not start on cylinder 0, the following error message is displayed:

  can't attach 
  labeled submirror to an unlabeled mirror 

  You must ensure that either all submirrors you plan to attach to a mirror start on cylinder 0, or none do.

  Starting cylinders do not have to be identical across all submirrors, but all submirrors must either include or not include cylinder 0.