Unix Administration

DMP tunable parameters Table: DMP parameters that are tunable shows the DMP parameters that can be tuned by using the vxdmpadm settune command. Table: DMP parameters that are tunable Parameter Description dmp_cache_open If this parameter is set to on , the first open of a device that is performed by an array support library (ASL) is cached. This caching enhances the performance of device discovery by minimizing the overhead that is caused by subsequent opens by ASLs. If this parameter is set to off , caching is not performed. The default value is on . dmp_daemon_count The number of kernel threads that are available for servicing path error handling, path restoration, and other DMP administrative tasks. The default number of threads is 10. dmp_delayq_interval How long DMP should wait before retrying I/O after an array fails over to a standby path. Some disk arrays are not capable of accepting I/O requests immediately after fail...

Tunable parameters for VxVM Table: Kernel tunable parameters for VxVM lists the kernel tunable parameters for VxVM. Table: Kernel tunable parameters for VxVM Parameter Description vol_checkpt_default The interval at which utilities performing recoveries or resynchronization operations load the current offset into the kernel as a checkpoint. A system failure during such operations does not require a full recovery, but can continue from the last reached checkpoint. The default value is 20480 sectors (10MB). Increasing this size reduces the overhead of checkpoints on recovery operations at the expense of additional recovery following a system failure during a recovery. vol_default_iodelay The count in clock ticks for which utilities pause if they have been directed to reduce the frequency of issuing I/O requests, but have not been given a specific delay time. This tunable is used by utilities performing operations such as resynchronizing...

Changing the values of tunables Tunables can be modified by editing the file /kernel/drv/vxio.conf for most VxVM kernel tunables. The system must be shut down and rebooted for the change to take effect. Warning: If you modify /kernel/drv/vxio.conf , make a backup copy of the file. For example, a single entry has been added to the end of the following /kernel/drv/vxio.conf file to change the value of vol_tunable to 5000: name="vxio" parent="pseudo" instance=0 vol_tunable =5000; Warning: Do not edit the configuration file for the vxspec driver, /kernel/drv/vxspec.conf . You can use the prtconf -vP command to display the current values of the tunables. All VxVM tunables that you specify in /kernel/drv/vxio.conf are listed in the output under the "System properties." heading for the vxio drivers. All unchanged tunables are listed with their default values under the "Driver properties" heading. The following sa...

Retrieving information about a DMP node The following command displays the DMP node that controls a particular physical path: # vxdmpadm getdmpnode nodename=c3t2d1s2 The physical path is specified by argument to the nodename attribute, which must be a valid path listed in the /dev/rdsk directory. The command displays output similar to the following: NAME STATE ENCLR-TYPE PATHS ENBL DSBL ENCLR-NAME =============================================================== c3t2d1s2 ENABLED T300 2 2 0 enc0 Use the -v option to display the LUN serial number and the array volume ID. # vxdmpadm -v getdmpnode nodename=c2t16d11s2 NAME STATE PATHS ENBL DSBL ENCLR-NAME SERIAL-NO ARRAY_VOL_ID ==================================================================================== c2t16d11s2 ENABLED 4 4 0 HDS9500-ALUA0 D600172E015B E01 Use the enclosure attribute with getdmpnode to obtain a list of all DMP ...

Setting customized names for DMP nodes The DMP node name is the meta device name which represents the multiple paths to a disk. The DMP node name is generated from the device name according to the VxVM naming scheme. See Disk device naming in VxVM . You can specify a customized name for a DMP node. User-specified names are persistent even if names persistence is turned off. To specify a custom name for a DMP node Use the following command: # vxdmpadm setattr dmpnode dmpnodename name= name You can also assign names from an input file. This enables you to customize the DMP nodes on the system with meaningful names. To assign DMP nodes from a file Use the script vxgetdmpnames to get a sample file populated from the devices in your configuration. The sample file shows the format required and serves as a template to specify your customized names. To assign the names, use the following command: # vxddladm assign names file= pathname

Enabling multipathing and making devices visible to VxVM Use this procedure to re-enable multipathing for a device, or to make a device visible to VxVM again. Warning: A reboot of the system may be required. To enable multipathing and make devices visible to VxVM Run the vxdiskadm command, and select Allow multipathing/Unsuppress devices from VxVM's view from the main menu. You are prompted to confirm whether you want to continue. Select the operation you want to perform from the following options: Option 1 Makes all paths through a specified controller visible to VxVM. Option 2 Makes specified paths visible to VxVM. Option 3 Makes disks visible to VxVM that match a specified Vendor ID and Product ID. Option 4 Removes a pathgroup definition. (A pathgroup explicitly define...

Disabling multipathing and making devices invisible to VxVM Use this procedure to prevent a device from being multipathed by theVxVM DMP driver ( vxdmp ), or to exclude a device from the view of VxVM. Warning: A reboot of the system may be required. To disable multipathing and make devices invisible to VxVM Run the vxdiskadm command, and select Prevent multipathing/Suppress devices from VxVM's view from the main menu. You are prompted to confirm whether you want to continue. Select the operation you want to perform from the following options: Option 1 Excludes all paths through the specified controller from the view of VxVM. These paths remain in the disabled state until the next reboot, or until the paths are re-included. Option 2 Excludes specified paths from the view of VxVM. Option 3 Excludes disks from the view of VxVM that match a specified Vendor ID and Product ID. Option 4 Defines a pathgroup for d...