I am trying to measure the speed of reading a given block size using the dd command. However depending on which input I use: a regular file (on the same device) or /dev/sdb1, I get some really different results.
Note:
- Freshly formated ext4
ATA device, with non-removable media
Transport: Serial, SATA Rev 3.0
- I did the same experiment with varying blocksizes, and up to 128K the phenomena is the same.
- The file pirate is 100G and filefrag reports: 57 extents found
Questions:
- Is this normal?
- I am wondering if the speed of repositioning the disk head to the beginning of a device is fast comparing to any file offset movement. because reading 512B should be elementary ...
Thanks a lot
Last edited by methyl; 07-03-2012 at 07:36 PM..
Reason: please use code tags
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