Steve, Jeff,
A write to a file will change the file size attribute in the directory entry, which will of course change the mod time on the directory itself.
In fact, if you don't have "atime update" turned OFF, even opening a file will change the directory mod time since the access time attribute for the file needs to be updated in the directory entry.
Remember, in WAFL all metadata lives in files. That includes directories. So ANY change to a directory entry will cause the modification time on the directory to be updated. This will in turn change the mod time on all relevant parent directories up to the root. On a traditional filesystem like NTFS or UFS this would be a performance disaster as it would generate lots of additional seeks, so they don't do it. However in WAFL an change to a file will cause all relevant metadata inodes up to the root inode to be rewritten [in new locations without seeks] anyway, without a performance cost.
Hope this helps.
Alan McLachlan Senior Systems Engineer Storage Management Solutions ASI Solutions www.asi.com.au Ph +61 2 6230 1566 Fax +61 2 6230 5343 Mobile +61 428 655644 e-mail amclachlan@asi.com.au
-----Original Message----- From: Steve Losen [mailto:scl@sasha.acc.virginia.edu] Sent: Thursday, 22 May 2003 7:30 AM To: Jeff Burton Cc: toasters@mathworks.com Subject: Re: Folder update time
Anyone know why DOT updates the modification time on a ntfs folder when a file in that folder is simply opened? This is not the way it works on our other NT systems. Is this a "feature", a bug, or just a difference between ntfs and wafl's interpretation of ntfs? I'm on a F880c running 6.3.1R1....and I'm a unix person so I may be missing the obvious, but I don't think so. Thanks,
Jeff Burton Storage Architect Abbott Laboratories EMAIL: Jeffrey.Burton@Abbott.com Dept. GB16/Bldg. AP14B-1 PHONE: 847-935-5778 100 Abbott Park Rd. FAX: 847-938-5824 Abbott Park, IL 60064-6042
My guess is that the application is doing more than a simple file open. Perhaps it is an editor that is creating a .bak file or something like that. As far as I know, to change the mod time of a directory (folder) you need to create, delete, or rename a file in the directory. Simply reading or writing an existing file does not change the directory mod time. An application could also explicitly set the mod time of the directory.
I can think of one other possibility, but I have doubts since this is a NTFS volume. If you create a directory with NFS, then it is not in unicode format (unless you specify an option to change this). The first time you access the directory via CIFS, it is converted to unicode, and this might also trip the directory mod time, but I don't know. Of course, this only happens once at the first CIFS access.
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support
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