APT_FILE_IMPORT_BUFFER_SIZE

Set the APT_FILE_IMPORT_BUFFER_SIZE environment variable to specify the size, in kilobytes, of the buffer for reading in files.

The default is 128 (that is, 128 KB). It can be set to values from 8 upward, but is clamped to a minimum value of 8. That is, if you set it to a value less than 8, then 8 is used. Tune this upward for long-latency files (typically from heavily loaded file servers).