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What is buffer pool extension in SQL Server?
Introduced in SQL Server 2014 (12. x), the buffer pool extension provides the seamless integration of a nonvolatile random access memory (that is, solid-state drive) extension to the Database Engine buffer pool to significantly improve I/O throughput.
What is database buffer pool?
A buffer pool is an area of main memory that has been allocated by the database manager for the purpose of caching table and index data as it is read from disk. Each new database has a default buffer pool defined, called IBMDEFAULTBP.
What is buffer cache hit ratio in SQL Server?
Buffer cache hit ratio Indicates the percentage of pages found in the buffer cache without having to read from disk. The ratio is the total number of cache hits divided by the total number of cache lookups over the last few thousand page accesses. After a long period of time, the ratio moves very little.
How do I test a SQL buffer pool?
SQL Server can tell you how many of those pages reside in the buffer pool. It can also tell you which databases those pages belong to. We can use sys. dm_os_buffer_descriptors to provide this information as it returns a row for each page found in the buffer pool at a database level.
What is stored in InnoDB buffer pool?
The InnoDB buffer pool is a key component for optimizing MariaDB. It stores data and indexes, and you usually want it as large as possible so as to keep as much of the data and indexes in memory, reducing disk IO, as main bottleneck.
What is buffer hit ratio?
The buffer hit ratio (BHR) indicates the current ratio of buffer cache hits to total requests, essentially the probability that a data block will be in-memory on a subsequent block re-read. A correctly tuned buffer cache can significantly improve overall database performance.
What is the largest memory consumer in the buffer pool?
As I would expect the Buffer Pool is the largest consumer of memory within the instance with just over 4.5Gb allocated. The lock manager is next with just over 1Gb allocated for lock resources and the remaining clerks relate to allocations for the query plan.
What is the purpose of buffer cache?
In SQL Server, the buffer cache is the memory that allows you to query frequently accessed data quickly. When data is written to or read from a SQL Server database, the buffer manager copies it into the buffer cache (aka the buffer pool).
What do you need to know about SQL server buffer pool extension?
If you have read about new features introduced in SQL Server 2014, then you must have learned about the Buffer Pool Extension feature. This feature which will help DBAs to extend the Buffer Pool size beyond available physical RAM. One can easily compare this to the page file for an operating system – but it is even better.
How is SSD used in a buffer pool?
SSD storage is used as an extension to the memory subsystem rather than the disk storage subsystem. That is, the buffer pool extension file allows the buffer pool manager to use both DRAM and NAND-Flash memory to maintain a much larger buffer pool of lukewarm pages in nonvolatile random access memory backed by SSDs.
What happens if buffer pool is not enabled?
Buffer pool extension is not enabled. Then the only way to get rid of the error is to restart SQL Service; doing that on production database server is not an option. In summary, we can say that buffer pool extension introduces another level of cache.
What should be the size of the buffer pool?
The buffer pool extension size can be up to 32 times the value of max_server_memory. We recommend a ratio between the size of the physical memory (max_server_memory) and the size of the buffer pool extension of 1:16 or less. A lower ratio in the range of 1:4 to 1:8 may be optimal.