How to tell if CF card is faulty 3313

Mathew J. Newton

Well funnily enough I have another CF card that's playing up which I need to test so I tried badblocks. I tried it without the -p 10 since apart from taking a lifetime to run, flash memory can only do a limited number of write cycles. badblocks didn't show any problems so I tried to re-test by hand (as it were). I did:

# dd if=-dev-urandom of=test.file bs=1M count=256 256+0 records in 256+0 records out

Avebury:-home-john-pix-cftest # ll total 262412 drwxr-xr-x 2 root root 4096 2005-04-06 11:59 . drwxr-xr-x 87 john users 4096 2005-04-06 11:58 .. -rw-r--r-- 1 root root 268435456 2005-04-06 12:01 test.file (file is 256M i.e. 256 * 1024 * 1024 - same as 256M CF card isn't it?)

# dd if=test.file of=-dev-sda1 bs=1M dd: writing `-dev-sda1': No space left on device 249+0 records in 248+0 records out

can be mistaken about a "256M" card being 256*1024*1024 - it's still more than 256,000,000. I'm buttuming it successfully wrote 248 records and failed on the 249th)

# dd if=-dev-sda1 of=test.out bs=1M 248+1 records in 248+1 records out

(Why am I getting 248+0 when writing, 248+1 when reading back? What does the + figure mean? man dd and info coreutils dd invocation doesn't tell me.)

# dd if=test.file of=test.248 bs=1M count=248 248+0 records in 248+0 records out

# ll test.out test.248 -rw-r--r-- 1 root root 260046848 2005-04-06 12:27 test.248 -rw-r--r-- 1 root root 260292608 2005-04-06 12:26 test.out

(Something wrong here: why am I getting different file sizes? Maybe it's related to dd reporting 248+1 records for some operations and 248+0 for others.)

I then tried truncating both files to 247M and comparing, and found no difference, so looks as if the fault isn't showing up with this test either - seems to be intermittent.

Can anyone help me with the + number issue with dd though?