Here are some speed results of speed of two sd cards on two different Raspberry Pis (old 256MB and new 512MB one). I followed methodology listed on http://elinux.org/RPi_SD_cards:
Write speed sync; time dd if=/dev/zero of=~/test.tmp bs=500K count=1024; time sync Read speed dd if=~/test.tmp of=/dev/null bs=500K count=1024
And here are the results:
SanDisk Extreme class 10 UHS-1 45MB/s New Raspberry Pi: write: 524288000 bytes (524 MB) copied, 27.2083 s, 19.3 MB/s read: 524288000 bytes (524 MB) copied, 22.5482 s, 23.3 MB/s
Old Raspberry Pi: write: 524288000 bytes (524 MB) copied, 28.5079 s, 18.4 MB/s read: 524288000 bytes (524 MB) copied, 22.6449 s, 23.2 MB/s
Centon class 4 (cheap card from Walmart)
New Raspberry Pi: write: 524288000 bytes (524 MB) copied, 112.908 s, 4.6 MB/s read: 524288000 bytes (524 MB) copied, 30.2082 s, 17.4 MB/s
Old Raspberry Pi: write: 524288000 bytes (524 MB) copied, 106.991 s, 4.9 MB/s read: 524288000 bytes (524 MB) copied, 27.7869 s, 18.9 MB/s
Result: spend five dollars/pounds more and buy a proper card.
