Guidelines for Solstice DiskSuite/Solaris Volume Manager Software

Consider the following points when you plan Solstice DiskSuite/Solaris Volume Manager configurations.

• Local metadevice or volume names – The name of each local Solstice DiskSuite metadevice or Solaris Volume Manager volume must be unique throughout the cluster and cannot be the same as any device ID (DID) name.

• Mediators – Each diskset configured with exactly two disk strings and mastered by exactly two nodes must have Solstice DiskSuite/Solaris Volume Manager mediators configured for the diskset. A disk string consists of a disk enclosure, its physical disks, cables from the enclosure to the node(s), and the interface adapter cards. You must configure each diskset with exactly two nodes acting as mediator hosts. You must use the same two nodes for all disksets requiring mediators and those two nodes must master those disksets. Mediators cannot be configured for disksets that do not meet the two-string and two-host requirements. See the mediator(7D) man page for details.

• /kernel/drv/md.conf settings – All Solstice DiskSuite metadevices or Solaris Volume Manager volumes used by each diskset are created in advance, at reconfiguration boot time, based on configuration parameters found in the /kernel/drv/md.conf file.

  You must modify the nmd and md_nsets fields as follows to support a Sun Cluster configuration:

  • md_nsets – The md_nsets field defines the total number of disksets that can be created for a system to meet the needs of the entire cluster. You must set the value of md_nsets to the expected number of disksets in the cluster, plus one to allow Solstice DiskSuite/Solaris Volume Manager software to manage the private disks on the local host (that is, those metadevices or volumes that are not in the local diskset).

    The maximum number of disksets allowed per cluster is 32 (31 disksets for general use plus one for private disk management). The default value of md_nsets is 4.

  • nmd – The nmd field defines the number of metadevices or volumes created for each diskset. You must set the value of nmd to the predicted highest value of metadevice or volume name used by any one of the disksets in the cluster. For example, if a cluster uses 10 metadevices or volumes in its first 15 disksets, but 1000 metadevices or volumes in the 16th diskset, you must set the value of nmd to at least 1000. Also, the value of nmd must be large enough to ensure that there are enough numbers for each DID name and for each local metadevice or volume name to be unique throughout the cluster.

    The highest allowed value of a metadevice or volume name per diskset is 8192. The default value of nmd is 128.

  Set these fields at installation time to allow for all predicted future expansion of the cluster. Increasing the value of these fields after the cluster is in production is time consuming because it requires a reconfiguration reboot for each node. Raising these values later also increases the possibility of inadequate space allocation in the root (/) file system to create all of the requested devices.

  At the same time, keep the value of the nmd field and the md_nsets field as low as possible. Memory structures exist for all possible devices as determined by nmd and md_nsets, even if you have not created those devices. For optimal performance, keep the value of nmd and md_nsets only slightly higher than the number of metadevices or volumes you will use.

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  Caution –

  All cluster nodes must have identical /kernel/drv/md.conf files, regardless of the number of disksets served by each node. Failure to follow this guideline can result in serious Solstice DiskSuite/Solaris Volume Manager errors and possible loss of data.

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  See “System and Startup Files” in Solstice DiskSuite 4.2.1 Reference Guide or “System Files and Startup Files” in Solaris Volume Manager Administration Guide for more information about the md.conf file.