--On 07 November 2005 17:14 +0100, Didier Wiroth wrote:
I've build an image file with opensoekris for 256 mb sandisk
compactflash. The writing of the image file takes very long (102188
bytes/sec), see the output below (I interupted it after 20 minutes).
Give dd a larger blocksize.
CF works in blocks of usually 16KB(128Kbit) - I think you need the
card's datasheet to tell what this is, unless you test it empirically
(e.g. dd with different size blocks and see when it reaches it's best
transfer rate).
If you only send the card 512 byte blocks at a time, afaik the card has
to erase, copy previous contents and append 512 bytes, repeatedly until
each 'card-block' is full. Doing this kills performance, and won't help
the life of your card (though they last pretty well anyway).
How long should it normally take to write a 256mb to a compactflash
card? For me it takes about 42 minutes, is that normal?
It depends on the particular CF card, and the speed between the adapter
and PC (e.g. USB2 or not). But the erase-write-read cycle of a
too-small block size will almost certainly hide this.
