I have posted a new SdFat beta - SdFatBeta20121020.zip Google Code Archive - Long-term storage for Google Code Project Hosting..
This beta supports AVR boards and the new ARM Teensy 3.0 board Teensy 3.0 + header : ID 1044 : $19.95 : Adafruit Industries, Unique & fun DIY electronics and kits.
Performance is greatly improved for large reads and writes.
The following benchmarks were done using this ATP 1GB Industrial Grade SD card http://www.newegg.com/Product/Product.aspx?Item=9SIA12K0CT6829.
The results are in increasing order of performance.
Mega 2560 using the standard Arduino SD.h library with 4096 byte reads and writes.
File size 5MB
Buffer size 4096 bytes
Starting write test. Please wait up to a minute
Write 265.95 KB/sec
Maximum latency: 84184 usec, Minimum Latency: 14144 usec, Avg Latency: 15388 usecStarting read test. Please wait up to a minute
Read 314.07 KB/sec
Maximum latency: 14752 usec, Minimum Latency: 13020 usec, Avg Latency: 13035 usec
Mega 2560 using the new SdFat library with 4096 byte reads and writes.
File size 5MB
Buffer size 4096 bytes
Starting write test. Please wait up to a minute
Write 658.38 KB/sec
Maximum latency: 65816 usec, Minimum Latency: 6036 usec, Avg Latency: 6210 usecStarting read test. Please wait up to a minute
Read 616.40 KB/sec
Maximum latency: 7624 usec, Minimum Latency: 6628 usec, Avg Latency: 6638 usec
Teensy 3.0 at 96 MHz using the new SdFat library with 4096 byte reads and writes.
File size 5MB
Buffer size 4096 bytes
Starting write test. Please wait up to a minute
Write 1776.44 KB/sec
Maximum latency: 65790 usec, Minimum Latency: 2146 usec, Avg Latency: 2300 usecStarting read test. Please wait up to a minute
Read 2037.15 KB/sec
Maximum latency: 2356 usec, Minimum Latency: 1999 usec, Avg Latency: 2008 usec
Here is my best Teensy 3.0 result using an old Corsair 1GB SD (no longer available) with 8192 byte reads and writes.
File size 10MB
Buffer size 8192 bytes
Starting write test. Please wait up to a minute
Write 2002.05 KB/sec
Maximum latency: 6777 usec, Minimum Latency: 4007 usec, Avg Latency: 4089 usecStarting read test. Please wait up to a minute
Read 2121.47 KB/sec
Maximum latency: 4231 usec, Minimum Latency: 3853 usec, Avg Latency: 3860 usec