Grass Valley K2 Media Client System Guide Oct.10 2006 - Manual (Page 106)

106 K2 Media Client System Guide September 7, 2006
Chapter 7 External Storage
About load balancing
When you purchase a K2 Storage System to provide the shared storage for your K2
Media 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 Media Clients. The bit rates, media formats, and
ratio of record channels to play channels all effect your bandwidth requirements.
As you add your K2 Media Clients to the K2 Storage System, you must assign a
bandwidth value to each K2 Media Client. This value is based on your intended use
of the channels of that K2 Media 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 Media
Client. The K2 System Configuration application takes that bandwidth value and load
balances it across the K2 Storage System, so that the K2 Media 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 external storage is sized, you have sufficient
bandwidth for all your K2 Media Clients.
Load balancing is important for the K2 Storage System because of the relative
bandwidth constraints inherent in Gigabit Ethernet and the iSCSI protocol. The K2
Storage System 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 Storage System 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 Storage System, the K2 System Configuration application
assigns a K2 Media Client to a specific TOE and keeps track of the bandwidth so
subscribed to each TOE. A single K2 Media Client can only subscribe to a single
TOE. However, a single TOE can have multiple K2 Media Clients subscribed to it.
The K2 System Configuration application assigns K2 Media Clients to each TOE,
filling them until their subscription is full.
You should add your highest bandwidth K2 Media Clients first to the K2 Storage
System, so that the K2 System Configuration application can distribute them equally
across the available TOEs. Then when you add the lower bandwidth K2 Media
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 Media Client and increase its bandwidth
requirements, you risk oversubscribing the TOE to which that K2 Media 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 Storage
System again if you must increase the bandwidth requirements of a K2 Media Client.
Contact your Grass Valley representative for help with load balancing. To stay under
the total bandwidth limit of the K2 Storage System, you might have to decrease the
bandwidth requirements of another K2 Media Client. In any case you must again load
balance.