topic Re: ZIP limitation? in Operating System - OpenVMS

ZIP limitation?

Art Wiens — Tue, 25 Oct 2005 10:47:41 GMT

I am using Zip 2.3 (November 29th 1999) on Alpha v7.2-2 . I have been busy zipping unmaintained directories chock full of 3 - 10 block text files. Several directories have had 10,000+ files and went without issue. Next in line is a particular directory with over 45,000 files in it!!

I start ZIP and get no error message or indication that anything bad is happening ... process is doing "lots" of io, consuming cpu etc. but is now taking over 3 hours to even start adding files to a new zip file. It has no files open, no ZIP file created yet.

Is 45,000 too many files for ZIP?

Art

Re: ZIP limitation?

Arch_Muthiah — Tue, 25 Oct 2005 11:02:27 GMT

Please make sure your have the latest version of zip from the following HP link, where you can find all the latest ZIP, UNZIP packages.

http://h71000.www7.hp.com/openvms/freeware/freeware.html

Re: ZIP limitation?

Ian Miller. — Tue, 25 Oct 2005 11:03:13 GMT

Zip has a 2Gb file size limit - parhaps you are running into that?

Accessing a directory of that size is going to be slow whatever you are doing.

Re: ZIP limitation?

Art Wiens — Tue, 25 Oct 2005 11:34:55 GMT

Archunan: The version I'm using is the same as what's on the Freeware v2.3 .

Ian: No it shouldn't be close to 2G, tons of files but they're all small.

It finally did "start" after about 4 hours. What's it doing during this initial period? Obviously it must be "reading" the source files, but I don't see any open files for this process other than the executable.

I guess if I had to deal with 45,000 things, I might take a bit of time upfront to plan what I was going to do first ;-)

Cheers,
Art

Re: ZIP limitation?

Ian McKerracher_1 — Tue, 25 Oct 2005 11:59:35 GMT

Hello Art,

Have a look at this link. It probably isn't the cause of your problem but it may be of interest.

http://www.techiegroups.com/archive/index.php/t-54389.html

Regards,

Ian

Re: ZIP limitation?

Art Wiens — Tue, 25 Oct 2005 13:15:03 GMT

Thanks Ian. I did notice that it's creating the temporary ZI*.* file in my local directory - once it gets going. In my case though, several hours went by before it even opened the ZI file. Another 1.5 hours to add all 45,763 files into it.

Art

Re: ZIP limitation?

Steven Schweda — Tue, 25 Oct 2005 13:58:17 GMT

> Please make sure your have the latest
> version of zip

This is good advice.

> from the following HP link, where you
> can find all the latest ZIP, UNZIP
> packages.

This is no better advice today than it was a
while ago. As I enjoy reminding people,
repeatedly in some cases, the latest
released versions are Zip 2.31 and UnZip
5.52, and the source kits are normally
available at or near:

http://www.info-zip.org/

Zip 2.31, for example, puts the "ZI*."
temporary file in the right place. If your
actual archive will be on a diferent device,
Zip 2.3 will need to copy the whole thing
after it's done, while Zip 2.31 will simply
(and quickly) rename it.

I wouldn't bet that a newer Zip would work
any faster on a large number of files, but
I'd be interested to learn whether it does.
I doubt that anyone has tried a test like
this, so there could easily be some
previously unnoticed slow code in there.

What's the Zip command used? There could,
for example, be a problem in VMS wildcard
processing. I assume that you're not
explicitly specifying all 45000 file names.

I've forgotten. Is VMS V7.2-2 too old for
the latest directory caching improvement?

It shouldn't be '"reading" the source files',
but it should be looking for them, as it
does need a list. If the directory look-ups
are slow, then Zip may be doomed to a
certain amount of undesirable sloth.

P.S. If you hit the 2GB limit, let me know.

Re: ZIP limitation?

Art Wiens — Tue, 25 Oct 2005 14:08:07 GMT

The command was:

$ zip "-Vwj" zipfile.zip $1$dga77:[dir.subdir]*.*;*

I was not in the source directory when I issued the command, the source directory contained 45,763 files. The resulting zip file ended up being 458,398 blocks.

Art

Re: ZIP limitation?

Steven Schweda — Tue, 25 Oct 2005 14:42:44 GMT

Ok. It seems that VMS V7.2 was where the
directory cache improvement was made, so I
probably can't blame that. Of course, and I
quote:

[T]he OpenVMS Wizard cannot and does not
recommend storing large numbers of files
in a single (very large) directory.

http://h71000.www7.hp.com/wizard/wiz_5241.html

If you don't specify a non-default device
for the archive file itself
("dev:[dir]zipfile.zip"), then that
particular fix in Zip 2.31 won't affect you.
Other I/O speed improvements might, however,
so I'd still suggest using the newer version.
200MB is not 2GB, but it does take some
little while to write it. But in your case,
the prep time seems to swamp the I/O time.

When I get really bored, I may have a look at
the wildcard code to see if it does something
especially lame.

Wake me if things get any worse.

Re: ZIP limitation?

Steven Schweda — Tue, 25 Oct 2005 21:52:17 GMT

For a good time, I made a short command
procedure to create N similarly named files
("A_nnnnnn.dat", nnnnnn = "000001", ...) in
a directory. On an otherwise idle XP1000
(500MHz):
N = 10000, t = 0:22:41
N = 50000, t = 2:56:04

Looks non-linear to me.

Given that it takes three hours just to
create 50000 such small files, I'd bet that
doing any significant directory work on that
mess would be comparably slow, and thus that
there's not much hope of speeding up Zip in
this situation.

See also:

http://groups.google.com/group/comp.os.vms/browse_thread/thread/a57ade02d8aae46e

Re: ZIP limitation?

Willem Grooters — Wed, 26 Oct 2005 05:12:55 GMT

Art,

I'm not certain this applies to your problem:
If you do:

1. $ zip "-Vwj" zipfile.zip $1$dga77:[dir.subdir1]*.*;*
2. $ zip "-Vwj" zipfile.zip $1$dga77:[dir.subdir2]*.*;*

and so on, so you're adding files beyond an existing one. This takes time since the EXISTING data needs to be copied first, I don't know how efficient zip will do this. Uisng this, each addition will take more and more time.
Since you omit the directory information (-j option) it might be that each addition might mean that checks need to be done - and this requires scanning thealready stored information. Again, the more files you have in the archive, the longer it would take.

If next is a directory of 45000 files, you can expect low performance for several reasons: the size of the directory itself will add to the already heavy processing.

Consider to make a separate zip of each directory, and zip these all into one.

1. $ zip "-Vwj" zipfile1.zip $1$dga77:[dir.subdir1]*.*;*
2. $ zip "-Vwj" zipfile2.zip $1$dga77:[dir.subdir2]*.*;*

...
lastL
$ zip "-V" allzips.zip zipfile*.zip

Willem

Re: ZIP limitation?

Peter Barkas — Wed, 26 Oct 2005 09:23:13 GMT

I have experience of the performance difference between the two approaches described by Willem.

I was zipping about 40-60 files totalling about 1.5gb or so. Doing them all at once was fine but incrementally adding each one separately was much much slower.

Re: ZIP limitation?

Art Wiens — Wed, 26 Oct 2005 10:04:01 GMT

Steven:

"[T]he OpenVMS Wizard cannot and does not
recommend storing large numbers of files
in a single (very large) directory."

I'll try and mention that to the long gone application programmers! ;-)

That's why we call them "legacy" systems.

Willem:

No that doesn't apply, I'm zipping individual directories to new zip archives.

Cheers,
Art

Re: ZIP limitation?

Steven Schweda — Wed, 26 Oct 2005 13:27:11 GMT

> I'll try and mention that [...]

Slap 'im around a little for me, too.

> That's why we call them "legacy" systems.

Some legacy.

I recall some suggestions in comp.os.vms a
while ago, involving dispersing the files
from the one over-full directory into
multiple (less over-full) directories, and
creating a search-list logical name which
points to the list of new directories.

New files are still a problem, as they keep
getting put into the first directory in the
list, but finding the old files could be
faster.

This assumes that the directory name is not
hard-coded into the "legacy", of course.

Thoroughly re-engineering an application
without actually changing it can be tricky.
Of course, if "unmaintained" means "never to
be looked at again", you may be happier just
suffering for a while with slow Zip.

I'm still pushing Zip 2.31, however, as it's
better, even though it won't solve your big
problem.

Re: ZIP limitation?

Art Wiens — Wed, 26 Oct 2005 15:08:07 GMT

>> I'll try and mention that [...]

> Slap 'im around a little for me, too.

If they were still around it might be a closed fist! :-O

>> That's why we call them "legacy" systems.

> Some legacy.

Perhaps "inheritance" is a better analogy, but grannie didn't like me too much!

Ah well, like a fellow I used to work with always said:

"It's all pensionable time."

I'll give v2.31 a whirl.

Cheers,
Art

Re: ZIP limitation?

Willem Grooters — Thu, 27 Oct 2005 02:31:42 GMT

Legacy/Inheritance, meaning "oldfashioned"?

On a VMS system, it will take time (obviously) to DIR a directory of 10.000 files.
On a Unix system, listing a directroy of that size will tell you the commandbuffer is full and show you nothing else.

What do you prefer?

Willem

Re: ZIP limitation?

Steven Schweda — Thu, 27 Oct 2005 07:27:49 GMT

If you're foolish enouh to say "ls *", it may
fail. Do you think that a plain "ls" will
have any trouble? Have you tried it, or are
you just guessing?

I prefer less inane comments.

Re: ZIP limitation?

Art Wiens — Thu, 27 Oct 2005 08:30:02 GMT

Ok, I guess it's time to close this thread ;-)

VMS is a fine system. The way that some things were implimented by my predecessors could have been done a bit "cleaner" ... other things are quite clever and flexible.

Management keeps referring to it as a "sunsetting platform" except the sun is having a hard time rising on *nix, so I continue to try and patch holes and keep the boat afloat.

There is no "best" system/application out there.

Cheers,
Art