[sf-lug] SD card Performance

[Ken Shaffer]

At the last meeting, Eric raised the question of performance of
Kinston SD cards, and if the faster more expensive Ultra II(I?)s were worth
it.  Below are some read/write speeds I measured by copying cards
with dd.  The read speeds are copying to /dev/null, the write
speeds are actually the time to copy a card, so really include a
(much quicker) read of a Kingston 2G also.
The Kingston card has half the write speed, but was half the cost
of an Ultra II, while the read speeds were much closer. The advertised
15MB/sec of the Sandisk Ultra IIs were obviously the read speed!
Ken

Kingston 2G micro SD (not SDHC)
No speed claims on package, 128k erase block size
Boots 10.04 live media in 45 seconds
  (with the 3 quick returns to force a manual boot)
Whole disk copy using dd with 128k block size
Read speed = 13.3 MB/s
Write speed = 2.2 MB/s


Sandisk 2G SD UltraII
Claimed 15MB/sec on card, 32k erase block size
Boots 10.04 live media in 37 seconds
  (with the 3 quick returns to force a manual boot)
Whole disk copy using dd with 128k block size
Read speed = 16.3 MB/s
Write speed = 4.7 MB/s


Sandisk 2G SD UltraII
 Read Rate
$ date
Thu Sep  8 21:40:34 PDT 2011
$ sudo dd if=/dev/sdc of=/dev/null bs=128k
date
15088+0 records in
15088+0 records out
1977614336 bytes (2.0 GB) copied, 121.084 s, 16.3 MB/s
$ date
Thu Sep  8 21:42:38 PDT 2011

Write Rate
$ sudo dd if=/dev/sdc of=/dev/mmcblk0 bs=128k
date
14864+0 records in
14864+0 records out
1948254208 bytes (1.9 GB) copied, 411.056 s, 4.7 MB/s
$ date
Wed Sep  7 17:12:36 PDT 2011


Kingston 2G micro SD
Read Rate
$ sudo dd if=/dev/sdc of=/dev/null bs=128k
date
14864+0 records in
14864+0 records out
1948254208 bytes (1.9 GB) copied, 146.828 s, 13.3 MB/s
$ date
Thu Sep  8 21:25:34 PDT 2011

Write Rate varies from 2.1-2.2 MB/sec


Card Specific Data
Kingston 2G micro SD Card
./csd.py /sys/class/block/mmcblk0/device/csd
 Device size             =====  3715
 Device size multiplier  =====  7
 write block size        =====  1024
 write protect gp size   =====  1
 erase sector size       =====  128
 write speed factor      =====  4
 data transfer rate      =====  25MHz
read access time 1  =RAW=  46
 Max Rd Blk Len          =====  1024
Erase block size is 131072 bytes.

Sandisk Ultra II SD Card
 Device size             =====  3771
 Device size multiplier  =====  7
 write block size        =====  1024
 write protect gp size   =====  128
 erase sector size       =====  32
 write speed factor      =====  16
 data transfer rate      =====  25MHz
 read access time 1      =====  1.5ms
 Max Rd Blk Len          =====  1024
Erase block size is 32768 bytes.
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