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Kernel Log: Linux and hard disks with 4-KByte sectors

Feb 25, 2010, 00:02 (0 Talkback[s])
(Other stories by Thorsten Leemhuis)


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"In future, fdisk will arrange partitions in such a way that the new hard disks with 4-KByte sectors can achieve optimum performance – although, for now, users will still need to select fdisk's appropriate mode of operation manually. The developers of Realtime Linux have released new kernel versions, and the completion of and 2.6.33 is also approaching.

"Red Hat developer Karel Zak has released version 2.17.1 of the util-linux-ng tool collection used in many Linux distributions. It includes the "fdisk" command line program which, in its sector-based mode of operation, activated via the "-u" option, will from now on try to align partitions along megabyte boundaries in the same way as Windows 7 and Vista have done for some time. While this sounds like a minor change, it is essential for the gradually emerging large hard disks that work with 4-KByte sectors internally while, for compatibility reasons, externally pretending to use 512-Byte sectors like any other desktop hard disk released in the past 20 years.

"Linux file systems prefer to read and write in 4-KByte blocks, but older versions of fdisk arrange the first partition in such a way that it begins with the (512-Byte) sector 63 by default – which is right in the middle of a physical (4-KByte) sector. Writing 4 KBytes of data to the beginning of the partition consequently requires the hard disk to read two physical sectors of 4 KBytes, distribute the 4 KBytes of data across these two physical sectors, wait for the disks to do an extra round and then write the two sectors back to disk."

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