Steelhead Appliance Installation and Configuration Guide
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Granite Branch Storage
Overview of the Steelhead EX
Reactive prefetch
- The system observes block requests, applies heuristics based on these observations
to intelligently predict the blocks most likely to be requested in the near future, and requests those
blocks from the data center LUN in advance.
Policy-based prefetch
- Configured policies identify the set of blocks that are likely to be requested at a
given edge site in advance, and requests those blocks from the data center LUN in advance.
First request
- Blocks are added to the blockstore when first requested. Because the first request is
“cold,” it is subject to standard WAN latency.
System Architecture
At the data center, Granite Core integrates with existing storage systems and Riverbed implementations.
Granite Core connects dedicated LUNs with each Granite-enabled Steelhead EX appliance at the edge or
branch office.
Each Granite-enabled Steelhead EX appliance contains a blockstore that mirrors the datastore LUN. As a
result, the blockstore eliminates the need for separate block storage facilities at the branch office, as well as
all the associated maintenance, tools, backup services, hardware, service resources, and such.
The following diagram illustrates a generic deployment.
Figure 1-2. Generic Granite Deployment
The basic system components are:
Microsoft Windows Edge Server
- The branch-side server that accesses data from the Granite system
instead of a local storage device.
Blockstore
- The blockstore is a persistent local cache of storage blocks. Because each Granite-enabled
Steelhead EX appliance is linked to a dedicated LUN at the data center, the blockstore is generally
authoritative for both reads and writes.
In the previous diagram, the blockstore on the branch side syncs with LUN1 at the data center.
iSCSI Initiator
- The iSCSI initiator is the branch-side client that sends SCSI commands to the iSCSI
target at the data center.
Granite-enabled Steelhead EX appliance
- The branch-side component of the Granite system links the
edge server to the blockstore and links the blockstore to the iSCSI target and LUN at the data center.
The Steelhead provides general optimization services.
Data Center Steelhead
- The data center-side
Steelhead
peer for general optimization.
Granite Core
- The data center component of the Granite system. Granite Core manages block
transfers between the LUN and the Granite-enabled Steelhead EX appliance.
