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Oracle Tips by Burleson |
Oracle RAC Cache Fusion and I/O Bandwidth
Oracle RAC Cache Fusion uses a high-speed IPC interconnect to
provide cache-to-cache transfers of data blocks between instances in
a cluster. This is called data block shipping. This eliminates the
disk I/O and optimizes read/write concurrency. Block reads take
advantage of the speed of IPC and an interconnecting network.
The cache-to-cache data transfer is performed through the high speed
IPC interconnect. The Oracle Global Cache Service (GCS) tracks
blocks that were shipped to other instances by retaining block
copies in memory. Each such copy is called a past image (PI). The
GCS, via the LMSx background process, tracks one or more past image
versions (PI) for a block in addition to the traditional GCS
resource roles and modes. In the event of a node failure, Oracle can
reconstruct the current version of a block by using a saved PI.
The above book excerpt is from:
Oracle RAC
& Grid Tuning with Solid State Disk
Expert Secrets for High Performance Clustered Grid Computing
ISBN:
0-9761573-5-7
Mike Ault, Donald K. Burleson
http://www.rampant-books.com/book_2005_2_rac_ssd_tuning.htm |
