Can you let me know what is internal and external memories?
asked Mar 28, 2011 at 03:00 AM in Default
I, like Slick84, am not entirely sure what you mean by internal versus external memory. The closest thing I can think of to internal memory is a cache, which would make all other memory external.
CPUs tend to have a small cache that they work with which is physically internal to the processor die, this is distinct from the main system memory which is located on discrete hardware (normally DIMMs) and accessed by the system bus. Similarly, certain types of storage like harddrives sometimes have a cache to reduce physical accesses to the disk, and many video cards have their own onboard memory.
answered Mar 29, 2011 at 08:52 AM
Another way of looking at internal vs. external is RAM and DISK.
RAM is "internal" to the system and operates at nanosecond speed.
Drives are "external" and operate at millisecond speed (not counting SSDs in this).
Based on these definitions it is a benefit to perform operations in RAM - the faster medium - but for persistence you require the slower, external "memory".
answered Mar 30, 2011 at 05:16 AM
Another possibility with internal and external is in the realms of internal and external memory for a process.
This would be where SQL Server has N GB RAM (where N = Installed RAM - O/S Overhead). SQL Server then has access to the "internal" memory of the process, whilst there is still "external" memory out there being used by the O/S and other processes.
The terms internal and external are also used when talking about memory pressure, how an external process is starved of RAM and wants to (re)claim some from other processes. This happens on 32 Bit systems with SQL Server when memory management has not been performed properly.
answered Mar 30, 2011 at 06:19 AM
You can check about Memory structure in SQL Server
I'm not sure where you are getting your Internal/External terminology.
However, SQL Server Database Engine is a RAM hungry application. When it's not feeding off of the RAM, its going to the disk.
As common knowledge, its more expensive from a performance perspective to read from your disks (more i/o) than compared to the RAM (Random Access Memory).
On a 64-bit system, my current production SQL server which does 5+ million transactions a day has about 64gigs of ram.
answered Mar 28, 2011 at 12:53 PM