Writing entropy
Saturday, August 18, 2007
Q: How long does it take to write a 120 GB disk full with random data?
A: 15 hours, 2 minutes and 27 seconds.
Obviously this depends on the machine. For me it was going at just under 8 minutes per GB, others report around 5 minutes per GB. Also this was using /dev/urandom as input for dd, wich is obviously not really random. I don't even want to think about how long it would take using /dev/random.
4 comments:
Jesse said...
How many threads were you using, and did you have any background tasks helping to generate entropy?
Unknown said...
This was from a life CD (grml) using simply "dd if=/dev/urandom of=/dev/hda". So the aswer would be, 1 thread and no helper tasks.
Jesse said...
I've had to (on occasion) fill large amounts of disk/storage space fairly rapidly - reading off of /dev/urandom with $N threads with additional threads generating entropy (say, pinging the local NIC, reading dict/words) improves the write speed and can really generate multi-gb files in minutes.
Anonymous said...
It took me 13h to erase 120GB
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