How to tell if CF card is faulty 3314

John Stumbles

buttuming you're running a sufficiently recent kernel (2.6.x, for stable), look atsys-block-sda-sda1-size to get the size of the device, as the kernel sees it. Hard disk drive manufacturers measure disk sizes in si units instead of traditional computing units. (1KB to them is 1000 bytes, not 1024 bytes.) This means my "10.2GB" seagate drive actually only holds 9.6GB of data. (Flamewars of GiB vs GB aside, of course) It's possible that the manufacturer took advantage of the same marketing-freindly measuring system.

I'm not sure, but dd might not be counting partial records after an aborted write. (i.e. when the end of the disk is reached.) If that's the case, you're seeing a bug in your version of dd.

The y in "x+y records in-out" refers to a partial record. Since you're using a huge blocksize (1M), and the device's size apparently isn't a round number of MB, dd can't write a complete 249th record, typically either because there isn't enough space, or there isn't enough data with which to write.

This behavior is normal. If dd reads or writes a partial record, it *should* report "+1" instead of "+0".

You're on the right track. Judging from the differences in file sizes, the +1 referred to an additional 240K beyond the 248MB you specified by combining the bs argument with the count argument.

test.out is an image of all the data on your flash disk. test.248 is only the first 248MB, and lacks the final 240K.

no

You'll find that test.248 is identical to the first 248MB of test.out, because test.248 represents a subset of all the space on your disk, while test.out represents the entire disk.

HTH

Mike