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Number : 3849 Date : 2003-02-25 Author : Kan Yabumoto Subject : Re: /NX0 information only Size(KB) : 3
Hi all, Mellisa Evans reported: > All xxcopy command lines, in my batch files and Python > scripts that copy between operating systems, have had > the switch /nx0 added to them. > The speed of operation has improved dramatically. Here's a dirty secret of XXCOPY. I frequently check what people have to say about XXCOPY in various newsgroups. Fortunately, nearly all of them are quite positive in their description of XXCOPY. But, there has been one guy who recommends XXCOPY and then adds the comment, "XXCOPY is extremely slooooow!" Naturally, it bugged me a lot. I knew it was the /NX feature which slows things down. What I did not know until rather recently was how slow it could be. I was under the impression that when XXCOPY encounters a massive SFN-collisions (which became more and more problematic as people surf the web more often and they accumulate a lot of cookies in a directory), it slows down. I knew that and I was concentrating on when to give up the SFN-preservation scheme on a difficult case (which is an iterative process and is time consuming). More recently, a series of experiments revealed the startling result. The guy in the newsgroup was right. Ran on W98SE --------------------------------------------------------------- v.2.82.9 202,203 files 94 sec 4.6 sec/10000 files v.2.82.7 202,203 files 105 sec 5.2 sec/10000 files v.2.82.7 (/nx0) 202.203 files 90 sec 4.5 sec/10000 files v.2.82.9b 202,203 files 88 sec 4.4 sec/10000 files --------------------------------------------------------------- Ran on XP-Pro --------------------------------------------------------------- v.2.82.9 202,206 files 184 sec 8.1 sec/10000 files v.2.82.4 202,206 files 1266 sec 62.6 sec/10000 files v.2.82.4 (/nx0) 202,206 files 169 sec 8.3 sec/10000 files v.2.82.7 202,206 files 1099 sec 54.4 sec/10000 files v.2.82.7 (/nx0) 202.206 files 144 sec 7.1 sec/10000 files v.2.82.9b 202,206 files 134 sec 6.6 sec/10000 files --------------------------------------------------------------- What we did not know was the difference between Win9X and the NT-family OSes. Due to our set up in our labs, the Win98SE was our main OS with Win2K/XP as only a test bed. Now, we use the XP on a regular basis. So, until we started to use the XP as our main workhorse, XXCOPY's support (and testing) was more limited in the NT family environment. The technique that XXCOPY was using was much slower in the NT family OSes (I now know why). Starting with v.2.82.8 (which was retracted due to some problems), the re-coded routine in the /NX feature made a remarkable difference. In addition, if you use NTFS as the destination directory, XXCOPY uses an even more direct way to assign the SFN which is faster. Note: v.2.82.9b is still being tested in house only. I believe Melissa is still using a version that is older than v.2.82.9. In conclusion, Melissa is correct, but it is not necessary to worry about the /NX or /NX0 difference any longer if you use the latest version. This is one area the latest XXCOPY (v.2.82.9) makes a huge difference. Finally, I told the guy in the newsgroup that his harsh criticism (which was factually correct) no longer applies. Kan Yabumoto
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