Let’s take a closer look at the new CBRC features in VMware View 5.1
The Storage Accelerator is made up of two components. The first is a per VMDK digest file and the second is a global cache. The per VMDK digest file has a mapping for disk block number to hash value and the global cache has a mapping for hash value to actual data. The global cache is a reserved area of memory on the ESXi hosts. It is an in-memory dedupe cache that caches data based on the content hash of a disk block. When the VM issues a read request, we first use the digest file to get the hash value for a block and then consult the global cache to see if the block is in cached. Metadata for the digest file is maintained in memory. If there is hit, we go fetch the data from cache; if there is a miss, we go fetch the data from disk.