Difference between revisions of "HowTo Disable The "relatime" Method For File "atime" Updates"
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=='''relatime'''== | =='''relatime'''== | ||
| − | The [http://www.kernel.org/ Linux Kernel] supports the "'''Relative atime'''" ('''relatime''') update method. A "'''relatime'''" update will only updated the "'''atime'''" field if the previous "'''atime'''" is older than the "'''mtime'''" or "'''ctime'''" for the file. This technique can avoid a significant number of metadata "'''atime'''" updates. It's similar to the "'''noatime'''" mount option, but useful for applications like "[http://www.mutt.org/ mutt]" that need to know when a file has been read since it was last modified. | + | The [http://www.kernel.org/ Linux Kernel] supports the "'''Relative atime'''" ('''relatime''') update method. A "'''relatime'''" update will only updated the "'''atime'''" field if the previous "'''atime'''" is older than the "'''mtime'''" (modify time) or "'''ctime'''" (change status time) for the file. This technique can avoid a significant number of metadata "'''atime'''" updates. It's similar to the "'''noatime'''" mount option, but useful for applications like "[http://www.mutt.org/ mutt]" that need to know when a file has been read since it was last modified. |
'''NST''' has the "'''relatime'''" [http://www.kernel.org/ Kernel] option enabled by default. | '''NST''' has the "'''relatime'''" [http://www.kernel.org/ Kernel] option enabled by default. | ||
Revision as of 18:46, 4 August 2008
Overview
atime
The "Access time" field for a file within a given file system is know as: "atime". When a process reads a file, the "atime" field is updated with the current date/time for this access. Disabling "atime" updates using the "noatime" mount flag is probably one of the biggest performance tweak that a Linux administrator can make. An active Linux server is continually reading files which generates a significant number of "atime" updates. This translates to numerous metadata updates made to the file system by writes to the physical disk which can lead to poor I/O performance.
relatime
The Linux Kernel supports the "Relative atime" (relatime) update method. A "relatime" update will only updated the "atime" field if the previous "atime" is older than the "mtime" (modify time) or "ctime" (change status time) for the file. This technique can avoid a significant number of metadata "atime" updates. It's similar to the "noatime" mount option, but useful for applications like "mutt" that need to know when a file has been read since it was last modified.
NST has the "relatime" Kernel option enabled by default.
