HI Sachin, I just measured the actual use of the +FAT internal cache buffers.
In a test I sent and received 25 files using 3 FTP threads.
When copying to and from an SD-card, I used large (5MB) files, so 3 files were written and read simultaneously.
The result is surprising: in all cases, at most 9 buffers were used:
RAM-disk: Buffers 9 / 15
SD-Card : Buffers 9 / 128
So I would provide at least 9 x 512 ( =4608 ) bytes as caching memory. Later on, have a try with less if you like.
Note that in most cases, the internal caches are by-passed:
are optimised so that user-buffers are passed directly to the drivers
What is recommended size for cache memory size ?
9 x 512 bytes
What should be criteria to decide appropriate size ?
Look at how many files are open at the same time and how many tasks are accessing the same volumes (RAM-disk, SD-card). It should not get locked-up; task waiting for ither tasks.
There is a time-out when waiting for a free cache buffer: grep for
, by default 20 seconds.