I am using Super Tallent Pico C series 4 GB USB stick for Knoppix. It is very small in size and has very good reed speed. Here is the output of sudo hdparm -Tt /dev/sdb on my system:

/dev/sdb:
Timing cached reads: 1360 MB in 2.00 seconds = 680.29 MB/sec
Timing buffered disk reads: 70 MB in 3.05 seconds = 22.94 MB/sec

Here is some info regarding cached reads and buffered disk reads:

Cached reads:
"Perform timings of cache reads for benchmark and comparison pur‐
poses. For meaningful results, this operation should be
repeated 2-3 times on an otherwise inactive system (no other
active processes) with at least a couple of megabytes of free
memory. ###This displays the speed of reading directly from the
Linux buffer cache without disk access. This measurement is
essentially an indication of the throughput of the processor,
cache, and memory of the system under test.###"

Buffered disk reads:
"Perform timings of device reads for benchmark and comparison
purposes. For meaningful results, this operation should be
repeated 2-3 times on an otherwise inactive system (no other
active processes) with at least a couple of megabytes of free
memory. This displays the speed of reading through the buffer
cache to the disk without any prior caching of data. ###This mea‐
surement is an indication of how fast the drive can sustain
sequential data reads under Linux, without any filesystem over‐
head.### To ensure accurate measurements, the buffer cache is
flushed during the processing of -t using the BLKFLSBUF ioctl."