Grass Valley K2 Summit Storage Area Network v.7.1 - Manual (Page 343)

343 K2 Storage Area Network Installation and Service Manual 26 October 2009
Chapter 8 Configuring K2 clients on the K2 SAN
About load balancing
When you purchase a K2 SAN to provide the shared storage for your K2 clients, your
Grass Valley representative sizes the storage system based on your bandwidth
requirements. These bandwidth requirements are based on how you intend to use the
channels of your K2 clients. The bit rates, media formats, and ratio of record channels
to play channels all effect your bandwidth requirements.
As you add your K2 clients to the K2 SAN, you must assign a bandwidth value to each
K2 client. This value is based on your intended use of the channels of that K2 client.
There is a page in the K2 System Configuration application on which you enter
parameters such as channel count, bit rate, and track count per channel to calculate the
bandwidth value for a K2 client. The K2 System Configuration application takes that
bandwidth value and load balances it across the K2 SAN, so that the K2 client has
adequate bandwidth for its intended media access operations. When the bandwidth
values you enter in the K2 System Configuration application match the overall
bandwidth requirements upon which your K2 shared storage is sized, you have
sufficient bandwidth for all your K2 clients.
Load balancing is important for the K2 SAN because of the relative bandwidth
constraints inherent in Gigabit Ethernet and the iSCSI protocol. The K2 SAN uses a
mechanism called a TCP/IP Offload Engine (TOE) as a bridge across which all media
must travel between the iSCSI/Gigabit world and the SCSI/Fibre Channel world.
Each TOE has a limit as to how much bandwidth it can handle.
Depending on the level of your K2 SAN, you have one or more TOEs available for
load balancing. A TOE is hosted by the iSCSI interface board, which also provides
the Gigabit Ethernet connection.
As you configure your K2 SAN, the K2 System Configuration application assigns a
K2 client to a specific TOE and keeps track of the bandwidth so subscribed to each
TOE. A single K2 client can only subscribe to a single TOE. However, a single TOE
can have multiple K2 clients subscribed to it. The K2 System Configuration
application assigns K2 clients to TOEs, filling each TOE until its subscription is full.
You should add your highest bandwidth K2 clients first to the K2 SAN, so that the K2
System Configuration application can distribute them equally across the available
TOEs. Then when you add the lower bandwidth K2 clients, the K2 System
Configuration application can add them to the TOEs with bandwidth remaining.
It is important to realize that this load balancing does not adjust itself dynamically. If
you change your intended use of a K2 client and increase its bandwidth requirements,
you risk oversubscribing the TOE to which that K2 client is assigned. If this happens,
media access fails on all the clients assigned to the TOE.
To prevent oversubscription problems you should load balance your K2 SAN again if
you must increase the bandwidth requirements of a K2 client. Contact your Grass
Valley representative for help with load balancing. To stay under the total bandwidth
limit of the K2 SAN, you might have to decrease the bandwidth requirements of
another K2 client. In any case you must again load balance.
The K2 System Configuration application provides a report of iSCSI assignments,
which lists for each TOE the iSCSI clients assigned and their bandwidth subscription.