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What is buffer pool extension?
The buffer pool extension feature extends the buffer pool cache with nonvolatile storage (usually SSD). Because of this extension, the buffer pool can accommodate a larger database working set, which forces the paging of I/Os between RAM and the SSDs.
What is SQL Server buffer pool memory?
An SQL Server buffer pool, also called an SQL Server buffer cache, is a place in system memory that is used for caching table and index data pages as they are modified or read from disk. The primary purpose of the SQL buffer pool is to reduce database file I/O and improve the response time for data retrieval.
What is buffer pool and what is the need of buffer pool in Unix?
Buffer pool is collection of a buffers arrange in series. The kernel caches data in the buffer pool according algorithm called least recently used, after that it allocates a buffer for a disk block, it cannot use the same buffer again for another disk block until all other buffers have been used more recently.
Is there a buffer pool extension for SQL?
Buffer Pool Extension was released in SQL 2014 so it’s not new. It is also not advertised very much, but that’s not for lack of usefulness. RAM is far faster than SSD and certainly arm based disks, but most databases are too big to cache into RAM. BPE allows us to extend the buffer cache by storing clean pages on an SSD drive.
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.
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 page is not in buffer pool?
If the page is present at the Buffer Pool Extension, a copy of the page is made to the Buffer Pool and the page handle is returned to the requester. Notice that on that moment, the “same” page is located both in the Buffer Pool and its Extension. To complete the flow, let’s pretend that the page is not in the Buffer Pool Extension also.