Oracle Exadata System Software release 24.1.0 introduced the Exadata Storage Cache Statistics utility (ecstat), which provides real-time statistics about Exadata Smart Flash Cache.

The ecstat utility improves cache observability on each Exadata storage server, enabling valuable insight into various aspects of storage server performance, including:

• What is the balance of I/O operations across the main storage and Exadata Smart Flash Cache?

• How are different types of I/O operations (small reads, large reads, small writes, and large writes) serviced in the storage server?

• What is the I/O throughput provided by main storage and Exadata Smart Flash Cache?

• Is Exadata Smart Flash Cache performing well, or is it undersized?

The ecstat utility is conceptually similar to the Linux iostat utility, providing a periodic snapshot of I/O performance for each storage and cache device. Storage administrators can run ecstat on demand to understand real-time I/O performance. Additionally, Exawatcher includes ecstat output in its log files.

The ecstat utility in Oracle Exadata System Software release 25.1.0, contains the following enhancements:

• In addition to providing aggregated statistics about I/Os to main storage, ecstat also displays the top reasons why I/O was not satisfied using Exadata Smart Flash Cache. For example, the I/O was "marked as nocache", or the data was not cached as part of a "large write". This enhancement enables administrators to understand why some I/Os cannot be cached and also highlights I/Os that could benefit from a larger cache or redistribution of the available caching resources.

• In addition to displaying I/O performance statistics for each storage and cache device, ecstat also displays performance statistics for the top I/O consumers. The top consumers are displayed in two ways:

  • The top space consumers are ranked according to the total space allocated to each consumer in Exadata Smart Flash Cache. In this context, consumers can be databases that are explicitly specified in the IORM plan or they can be other entities that are implicitly included in the IORM plan, such as Exascale vaults and volumes.

  • The top IOPS consumers are sorted by total I/O throughput, in I/Os per second (IOPS). In this case, metadata embedded with each I/O identifies the consumers.

  By default, each list of top I/O consumers displays the top 10 consumers. However, ecstat can display up to 100 consumers in each list.

  These enhancements provides additional insight into the consumption of Exadata Smart Flash Cache resources, which can be used to adjust resource allocations or confirm that existing arrangements are working as expected.