PCFS mount options "noatime"/"atime" [PSARC/2007/415 FastTrack timeout 07/24/2007]

[Frank Hofmann]

On Wed, 18 Jul 2007, Don Cragun wrote:

>> Date: Wed, 18 Jul 2007 10:17:42 +0100
>> From: Peter Dennis - Solaris Sustaining Engineering <peter.dennis at sun.com>
>>
>> The Problem
>>         Flash-based removeable media can only perform a limited amount
>>         of write cycles. In addition to that, writes on such media are
>>         very slow (compared to reads). Since PCFS is frequently used
>>         on such devices ("memory sticks"), attempts should be made to
>>         minimize media write access whenever possible. Access timestamps
>>         are an easy target for that objective, because:
>>                 - FAT access timestamps are day-granular
>>                 - FAT access timestamps are optional as per FAT spec
>>
>>         In addition, UFS has had the "noatime" mount option since 1998.
>>         PCFS should have it as well.
>
> I wholeheartedly agree that the noatime mount option should be
> available on PCFS.  It isn't obvious to me, however, that it should be
> the default.  Note that since FAT access timestamps have 1 day
> resolution, the filesystem code is free to discard a write of an atime
> that has been marked for update if the new value matches the current
> value on the filesystem.  Noting once a day that a file has been
> accessed shouldn't grossly affect reliability of removeable media.
>
> Do Windows OSes have a noatime mount option?  If so, is it on by
> default?

It's the (nonconfigurable) default on MacOS, on your mobile phone's memory 
card, on your digial media player and not to forget your digital camera. 
Those do not record access time stamps, at least I have not found any that 
do.

I have made no detailed checks how Windows deals with removeable media as 
far as timestamp updates are concerned.

FrankH.

>
> - Don
>
>