When you do this, you are actually entering information about your nodes into the SDR. To enter, display, or change the setup information that is required for each node that is to either have or use virtual shared disks:
That opens a dialog window where you can enter pertinent information. The following information must be entered before you can create virtual shared disks or hashed shared disks:
Each node is identified by a node_number that represents its position in the SP rack.
The name of the adapter to be used for virtual shared disk communications with this node. All nodes must use the same adapter in a fully-connected network (all nodes must be able to send messages directly to each other).
The virtual shared disk component uses the adapter name and the related node number to get communication information associated with each node. The only supported adapter names are css0 and ml0.
ml0 provides data striping and recovery over multiple adapters. ml0 can be specified when the nodes support two switch adapters and a multilink IP address has been configured.
The virtual shared disk device driver implements an optional write-through cache of pinned kernel memory with a block size of 4KB. When the first cached virtual shared disk is configured on a node, the cache is created, containing the specified number of blocks. The minimum value is 1. The suggested value is 256, which results in a 1MB (1024KB) cache.
The number of buffers in the cache can be increased (using ctlvsd) up to this value. You cannot decrease the number of cache blocks. You can start over by unconfiguring all the virtual shared disks, changing the value of this number in the SDR, and then, when you configure the virtual shared disks, the initial number of virtual shared disk buffer cache blocks will be created. The suggested value is 256, resulting in a 1MB cache.
Specifies the maximum number of outstanding virtual shared disk requests originating on the node. The virtual shared disk device driver allocates this number of request blocks in pinned kernel memory the first time a virtual shared disk is configured. If the number is too small, local requests will queue up waiting for a request block to become available. The suggested value is 256. The size of the block is approximately 76 bytes.
Note that this information is not required for PSSP 3.2 or later releases and, if entered, the value will be ignored. It is, however, still a recognized value for releases prior to PSSP 3.2.
Specifies the maximum number of outstanding requests the virtual shared disk device driver will allow for each underlying logical volume. Each such request uses a pbuf. A pbuf is a little bigger than a buf structure, which is approximately 104 bytes. The virtual shared disk device driver allocates this number of pbufs in pinned kernel memory whenever a virtual shared disk that has this node as its primary is configured. The minimum value is 1. The suggested value for a primary or secondary node is 48. If the node is not going to be used as a primary or secondary, this value is irrelevant.
Note that this information is not required for PSSP 3.2 or later releases and, if entered, the value will be ignored. It is, however, still a recognized value for releases prior to PSSP 3.2.
The smallest buddy buffer a server will use to satisfy a request to a virtual shared disk. This value must be a power of 2 and greater than or equal to 4096. The suggested value is 4096 (4KB). For a 512-byte request, 4KB is clearly overkill but a buddy buffer is used only for the short period of time a remote request is being processed at the server node.
For more information on buddy buffers, see Buddy buffers.
The largest buddy buffer a server will use to satisfy a request. This value must be a power of 2 and greater than or equal to the min_buddy_buffer_size. The maximum value, and the suggested value, is 262144 (256KB). This value must be the same on all nodes within a system partition.
The buddy buffer is pinned kernel memory allocated when the virtual shared disk device driver is loaded. Loading occurs the first time a virtual shared disk is configured. Buddy buffers are freed when the last virtual shared disk is unconfigured. If you do not use the switch as your IP adapter, the size of the buddy buffer affects the number of remote requests the virtual shared disk server node can handle at one time. Remote requests can queue while waiting for a buddy buffer. The statvsd command and the Statistics notebook page of the IBM Virtual Shared Disk Perspective report this queuing as buddy buffer shortages. See Buddy buffers for more information about buddy buffers and how to determine how many to define. The suggested starting value is 232, which results in a 8MB buddy buffer size in combination with the suggested maximum buddy buffer size of 256KB. Tuning may be required on the switch; see SP Switch considerations when using the IP protocol for data transmissions.
The cluster_name is an optional name that must be set if this node is a server for concurrent virtual shared disk. For more information, see IBM concurrent virtual shared disks.
You can display and change some virtual shared disk node attributes which are kept in the SDR from the Node Attributes page of the Properties notebook at any time. You must reconfigure the virtual shared disk on the node before the changes take effect, however.
For more information about these options, see the full description of the action Designate as a VSD Node... in the online help or see the vsdnode command in the book PSSP: Command and Technical Reference.