Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

When I move a directory containing 900 MB in 4k files to another directory in the same filesystem, it takes nearly 1 minute and I hear the disk working. It's NTFS on Windows XP, the disk is quite fast (ST3100015 28AS) and works fine according to CrystalMark. I switched the antivirus off, and there's nothing else running (there's a lot of processes, but none doing any work).

WTF is it doing instead of changing two directory entries?

share|improve this question
Are you moving the entire directory, or just the inside files? And are you sure they are on the same filesystem? (Windows can mount another filesystem as a directory.) – grawity Feb 5 '11 at 18:59
Of course, the whole directory - that's why I wrote "changing two directory entries". And yes, there are definitively on the same filesystem - I created two new directories for the test, there's surely nothing mounted there. – maaartinus Feb 5 '11 at 19:06
up vote 2 down vote accepted

The erroneous assumption that you're making here is that moving subfolder items in an Explorer folder is a simple operation that involves merely modifying a couple of directory entries. It isn't. The low-level system call to move a file may be. But Microsoft Windows Explorer places layers on top of that. A "move" of a folder item may end up as being a "copy to new name then delete original" at the low-level rather than "rename this directory entry to that parent directory". Of course, the former is a much more expensive operation than the latter.

Why does Explorer do this? For starters, it's because a folder is not a directory. Not all "folders" that Explorer presents to the user are honest-to-goodness bona fide directories on a disc volume. Explorer has to, for example, work out what it means to "move" a directory from/to a virtual folder denoting remote files on a smart 'phone viewed over a Bluetooth FTP connection. That's not a simple rename operation at the raw system API level. The same is true of the Recycle Bin, whose actual expression at the raw file and directory level is filesystem-format-specific.

Explorer has an "engine" that works out what the "copy", "move", "rename", and "delete" actions for shell objects actually mean at the raw system API level. In the Explorer that comes in Windows NT 6.0 and later, the "move" operation is the IFileOperation::MoveItem() method. (It used to be the SHFileOperation() function.) There's a whole load of non-obvious stuff that goes on, even in what one might erroneously think could map be a simple "rename" system call, to provide the end-user-visible semantics of "moving" a subfolder item in Explorer. This includes all of the processing for all of the operation flags that can be set, which can include undo information recording, collision detection and autorenaming, checking last modification datestamps, overriding the old security descriptor, and updating progress dialogues.

If you want to test how long it takes to change a few directory entries around, use an application that does only that, and doesn't do all of the Explorer layers on top of it, such as the mv command.

share|improve this answer
That's it. Windows does a lot of fancy stuff in order to make my computer look like an i386. – maaartinus Mar 2 '11 at 18:58
You forgot to mention that Windows Explorer moves files recursively rather than atomically. It creates the target folder, then digs down in the subfolders to recreate the tree and then move the files one by one, subfolder by subfolder. – Wolf Mar 17 '11 at 15:06

It looks like Explorer has a compulsion to check if there are any files it doesn't want to move. This includes read-only files, executables, and whatever (as if a program I can re-install was more worth than my own files). This check seems to be the problem. When I move the directory using another program, it's much faster, but it still takes one to two seconds.

Could somebody kindly measure how long it takes on their computer? As an directory to play with I took a copy of the Windows directory.

share|improve this answer

If you have a tool installed that hooks file operations in Explorer, it can cause slowdowns. HardLinkShellExt can do this, others could too. See what shell extensions you have installed.

share|improve this answer
IIRC, there's nothing like this. The only thing slowing down my computer is the antivirus, and I switched it off for the test (made no difference). – maaartinus Feb 5 '11 at 23:02
Under what circumstances can HardLinkShellExt cause this exactly? – Syclone0044 Jan 5 '12 at 3:18
It's Smart Move feature can cause a large amount of I/O while it checks for junctions and links, since it has to walk the entire directory tree. That's not normal for a simple move or rename operation that stays on the same volume. In Explorer, that's normally an immediate operation. – afrazier Jan 5 '12 at 3:39

That pretty much is all it is doing, however, 4000 files is a lot, and will take a lot longer than one 900mb file.

Fire up YouTube and watch something whilst waiting or just be more patient!

share|improve this answer
Actually a move should be pretty quick - just the directory entries to update. @maaartinus did you move the files or copy then delete the originals? – Chris Feb 5 '11 at 18:18
But there's no reason for even looking at the files. The same command on Linux takes a fraction of a second, no matter how many files are there, since nobody cares. It like speaking about a paper pack slowed down by the amount of sheets therein. – maaartinus Feb 5 '11 at 18:23
@Chris: I moved them using the explorer. – maaartinus Feb 5 '11 at 18:24
@maaartinus - is 4k the file size or number of files (as Wil suggests). If it's the size, then 200,000+ files in one minute is not that bad. Try copying them too and see how long that takes. – Chris Feb 5 '11 at 18:30
@Chris: There are 4000 files and their total size is 900 MB. Copying takes about the same time. Stupid system. – maaartinus Feb 5 '11 at 18:39

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .