SdFat is setup to use these pins on Teensy 3.0:

11 - MOSI
12 - MISO
13 - SCK

The following are the SPI bus speeds for 

bool SdFat::begin(uint8_t chipSelectPin, uint8_t spiRate);

The higher speed is for F_BUS == 48 MHz and lower speed is for F_BUS == 24 MHz.

spiRate = 0 or 1  : 24 or 12 Mbit/sec
spiRate = 2 or 3 : 12 or 6 Mbit/sec
spiRate = 4 or 5 : 6 or 3 Mbit/sec
spiRate = 6 or 7 : 3 or 1.5 Mbit/sec
spiRate = 8 or 9 : 1.5 or 0.75 Mbit/sec
spiRate = 10 or 11 : 250 kbit/sec
spiRate = 12 or greater : 125 kbit/sec

Large reads and writes use fast multi-block SD read/write commands. For optimal
speed, use records that are a multiple of 512 bytes.

Run the bench.ino example to explore large read/write speed.

Replace this line:

#define BUF_SIZE 100

With a large size like this:

#define BUF_SIZE 4096

For best results the record size should be a power of two (512, 1024, 2048,
4096, 8192). In this case records will be aligned with FAT cluster boundaries.

Since Teensy is fast, increase the test file size by editing this line:

#define FILE_SIZE_MB 5

Run the PrintBenchmark.ino example to compare text formatting speed of
Teensy 3.0 with AVR boards.