Thread: n800, SD, SDHC, and storage
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Milhouse is offline Milhouse
2007-04-11 , 22:37
Posts: 3,401 | Thanked: 1,255 times | Joined on Nov 2005 @ London, UK
#22
300MB in 10-15 minutes doesn't sound right - something is wrong with the card, the card reader or the PC!

It's quite hard to benchmark the write speed on the N800 because of the internal OS filesystem buffering.

Using the following (utterly bogus) test...

Code:
/home/user # sync; time sh -c "dd if=/dev/zero of=/dev/mmcblk1 bs=1M count=128; sync; sync; sync;"
128+0 records in
128+0 records out
real    0m 20.64s
user    0m 0.00s
sys     0m 1.39s
...will "write" 128MB of data to a Transcend Class 2 8GB card (high speed, 4-bits wide) in 20.64 seconds (latest 3.2007.10-7 SDHC kernel) which works out at just over 6.2MB/s write speed.

I know the results from this test are incorrect, but it does go to show that you won't really see a great deal of difference between Class 2 and Class 4 write performance in day-to-day usage. The OS will finish writing the data asynchronously to the Class 4 card faster than it will the Class 2 card, but you're not likely to notice.

You should see a difference between Class 2 and Class 4 in a Windows PC as file transfers should be quicker with the Class 4 card, in which case your buying decision should be based on how often you intend to bulk copy data to the card when it is connected to a PC.

IMHO, the N800 isn't likely to see any benefit when using a Class 4 or faster card - Class 2 will be fine.