Virtual databases - Faster than Physical?

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  • Updated 2 years ago
When hearing that Delphix provisions "virtual data" many customers assume that whilst that sounds flexible it also sounds like it might be slower.

There are several reasons why Delphix Virtual Data is often faster to use than a traditional physical data copy.

All data managed by Delphix is compressed.   That means when we have to read and write data to physical disk we are always reading and writing compressed versions of data blocks.  If you assume only 50% compression that means we get to read or write twice the amount of data for the same I/O price.

The Delphix Engine also caches data across all Virtual Databases (VDBs).  Hence when supporting multiple VDBs from the same data source there is often a high cache hit ratio, reducing the number of physical reads that we have to perform   Since Delphix 4.3 we also now retain the blocks in our cache in compressed format doubling the effective size of the cache assuming a 50% compression ratio.

During a recent Proof of Concept a customer wanted to test the performance of a VDB against a physical copy of the same database using the same database server and the same physical storage.  They were running an Oracle database and used Oracle's Real Application Testing tool to capture a production workload and replay it with the same concurrency in their test environments.   The storage was connected to the database server using two 8 Gbit Fibre Channel links.  The workload presented around 1GB of network traffic (database server to storage) per second and generated 6MB of redo per second.  There were also many concurrent direct path reads.  Using Delphix 4.3 and Oracle direct NFS (dNFS) the Delphix VDB performed the same as the physical database.

So Delphix is not only faster at provisioning data copies, but those data copies may run faster than your existing non-production data copies.
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David Ruthven

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Posted 2 years ago

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