The SanDisk Ultra SDHC UHS-I Class 6 (4GB) cards can often be found for around $8. However, the Class 6, 4GB model is no longer listed on their website and has been replaced by newer models.
This particular SD card was rated as Class 6, and advertised as having quick transfers up to 30 MB/s. Of course there was a disclaimer that write speeds are lower than read speeds, etc.
A standard card reader on a desktop computer was used for the benchmark. It handles SDHC cards and is not UHS-I rated. As result, the full potential of this card may not be realized. However, a transfer rate of 30 MB/s is within it’s range as it uses a USB 2.0 bus to communicate with the built-in card reader.
The read speed came in around 18 MB/s and the write speeds were around 12 MB/s.
The 30 MB/s quick transfer was not achieved. However, a UHS-I rated device was not used and could be the difference.
On the other hand, the sustained write speed of around 12 MB/s was well above the certified Class 6 rating. A Class 6 SD card must be able to sustain a write speed of 6 MB/s. But based on the benchmark, this could easily be a Class 10 rated SDHC card.
Overall, the SanDisk Ultra SDHC UHS-I Class 6 (4GB) cards are a great value. The performance is on the high end for it’s price and Class 6 category. Just be wary of the claimed quick transfers up to 30 MB/s, which was full of disclaimers on the packaging.
Benchmarked below is the SanDisk Ultra SDHC UHS-I Class 6 (4GB) card formated to have a single fat32 partition.
fdisk -l /dev/sdd
Disk /dev/sdd: 3965 MB, 3965190144 bytes 3 heads, 32 sectors/track, 80672 cylinders, total 7744512 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000d59f7
Device Boot Start End Blocks Id System /dev/sdd1 2048 7743487 3870720 b W95 FAT32
Device Read Benchmark
hdparm -t /dev/sdd1
/dev/sdd1: Timing buffered disk reads: 54 MB in 3.00 seconds = 18.00 MB/sec
Device Write Benchmark: 1MB x 1000
dd if=/dev/zero of=tempfile bs=1M count=1000 conv=fdatasync,notrunc 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 86.0865 s, 12.2 MB/s
Device Write Benchmark: 10MB x 100
dd if=/dev/zero of=tempfile bs=10M count=100 conv=fdatasync,notrunc 100+0 records in 100+0 records out 1048576000 bytes (1.0 GB) copied, 84.9458 s, 12.3 MB/s
Device Write Benchmark: 100MB x 10
dd if=/dev/zero of=tempfile bs=100M count=10 conv=fdatasync,notrunc 10+0 records in 10+0 records out 1048576000 bytes (1.0 GB) copied, 85.8805 s, 12.2 MB/s
Device Write Benchmark: 500MB x 2
dd if=/dev/zero of=tempfile bs=500M count=2 conv=fdatasync,notrunc 2+0 records in 2+0 records out 1048576000 bytes (1.0 GB) copied, 87.5836 s, 12.0 MB/s
Device Write Benchmark: 1000MB x 1
dd if=/dev/zero of=tempfile bs=1000M count=1 conv=fdatasync,notrunc 1+0 records in 1+0 records out 1048576000 bytes (1.0 GB) copied, 90.8444 s, 11.5 MB/s