Zip files....drawbacks?

[Adcadet]

Hey all -
I'm running out of disk space
So I started rumaging around, and found a ton of things that I want to keep but rarely access. Out of curiosity I tried zipping them with Winzip, and have found that some things can be incredibly compressed. My old Outlook folder was 232 MB, and is down to half that. Some old webpages were comrpessed by 88%. I'm blown away. I didn't realize some things could be compressed so much. Of course I'm not surpized to see some things, like jpegs and .rm's don't comress much at all.

So...other than the need to unzip them if I need them later...is there a drawback?

Thanks!
Adcadet

 

[Will Rickards WT]

Corruption of the zip file can take out all your files.
But how often does that happen?

 

[Jake the Dog]

I use RAR compression personally. WinRAR is a great tool that allows you to test and repair damaged archives as well. compression is comparable to ZIP and you can choose different algorithms for different types of backups, eg multimedia type files. a more recent feature in WinRAR is the ability to store parity information across a series of volumes making data loss a thing of the past should some volumes go corrupt.

 

[Handruin]

I've found that winace can compress much better than winzip in certain conditions. You can also try compressing as a rar file.

From what I've seen, text files will usually compress 10:1. Images such as jpeg's won't compress much, but bitmaps will. Take a bitmap and compress it with winzip, and you may notice it becomes close to the same size as a jpeg equivilent.

From what I've seen it all depends on the media/file you are trying to compress. If you have raw video, it will compress greater than an MP2 or rm video. I believe the same concept is used for compression, the difference being that some are better at optimizing patterns at the cost of greater time on the CPU.

 

[Adcadet]

ok, so the two major drawbacks are CPU speed/time to open them (not a problem, since I rarely use these files and it seems my old and slow dual 1.2 GHz machine opens them fast enough), and risk of corruption. Can anybody elaborate on the corruption issue, especially vs. a bunch of files stored in one folder.

OK, back to memorizing cranial nerves.

Thanks,

Adcadet

 

[Handruin]

I'll have to dig up concrete info, but I believe that when you compress a file in winzip, there is a checksum value created and some type of header file that has a "map" (I think) of the compressed files.

If something small happens to the file header, every file inside could become useless. A virus at work killed many of our zip files even though we cleaned it. We could no longer extract the data.

Much to the same effect of having partitions on a hard drive. If the head crashes into the platters...you're practically SOL on all the data.

 

[Adcadet]

if I've got a bunch of files in a folder, can the folder info on the HD become corrupted, making all the files inside of it unrecoverable?

seriously, back to cranial nerves now!

Adcadet

 

[Handruin]

I don't see why the data couldn't become corrupted in a folder. It may depend on the file system type of the hard drive. NTFS may have ways of recovering from this, where as FAT/FAT32 may not. (I would have to use google to find out for sure)

 

[Mercutio]

NTFS disk compression is 1. Global within a compressed folder or disk.
2. Minimal in its impact on the system - very, very small increase in CPU utilization for a great deal of compression (how much depends on what you're compressing. I usually see 40% compression on a mix of image-laden Office docs), and 3. Completely transparent. No administrative effort = good thing.

NTFS compression is based on LZH. Not highly efficient but it (de)compresses very quickly.

 

[jtr1962]

Literally everything I backup on CD-RWs is in zip files. I really haven't had any problems with corruption. Sometimes it even makes sense to zip relatively uncompressible things like jpgs before backing them up on CD-RW. The reason here is that I've seen InCD choke when you have many folders with hundreds of files each, which is basically how my pictures are organized. By putting everything into a few .zip files you don't run into this problem. You also get quite a bit more on the disk than the rather poor compression ratio would indicate by avoiding cluster slack for tens of thousands of files.

 

[Adcadet]

NTFS disk compression is 1. Global within a compressed folder or disk.
2. Minimal in its impact on the system - very, very small increase in CPU utilization for a great deal of compression (how much depends on what you're compressing. I usually see 40% compression on a mix of image-laden Office docs), and 3. Completely transparent. No administrative effort = good thing.

NTFS compression is based on LZH. Not highly efficient but it (de)compresses very quickly.

Merc - are you suggesting that I use Window's compression rather than Winzip? As I was right clicking on files to compress them I saw that option, but was afraid that they might be unreadable on older Windows installations.

 

[timwhit]

I would use Winrar with multiple volumes and keep some parity sets around. Do a google search on par2 for more information on parity volumes. I think 50MB volumes are a good size, depending on what you are storing.

 

[Mercutio]

The compression state is within the file system and does not alter the file in any way. It changes the encoding used to store the file.
The compression state is only stored with the file if it's moved on the same volume/partiition.

RAR sucks Satan's ass. If the tools were anywhere near as usable, robust and well-integrated as ZIP, I might not have that opinion, but they aren't, and I regard having to break into an "unrar" tool as a disruption in my user experience. I unRAR'd a 450MB file over the weekend, on an XP2100, that took six hours to complete. That is in no way acceptable.

 

[timwhit]

Gimme a break, I unrared a 5 gig file on my XP1800 and it only took 20 minutes. There must be something wrong with your computer if it took that long.

 

[SteveC]

I unRAR'd a 450MB file over the weekend, on an XP2100, that took six hours to complete. That is in no way acceptable.

Six hours! What RAR program did you use? I can unrar CD size files with WinRAR 3.2 in about a minute on my PC.

 

[Mercutio]

WinAce.

The file in question contained around 12,000 image files (a large collection of stuff from someone's digital camera, in a slightly complex directory structure). Even if the idiot I got it from compressed the files, it shouldn't've taken that long. My working theory is that it's RAR.

I can zip the whole directory structure and unzip it again in under 10 minutes, even leaving compression on. I just checked.

There's nothing wrong with this computer.

 

[Mercutio]

So, 10 minutes after starting to RAR that directory - something that I accomplished in ~5 minutes with winzip - I'm just 1% done.

Whoops. It just flipped to 2%.
Wow. That's performance.

Remind me never to do this again.

 

[Mercutio]

4% now. It's really moving along.

I suppose I should point out that I'm using winRAR for compression, if that makes a difference.

 

[Adcadet]

mental note: return that copy of WinAce that I got for Merc for Christmas.

 

[Mercutio]

Merc doesn't celebrate xmas.

If I get lucky, I get the gift of triple overtime, which I can sometimes guilt-trip a client into paying since I'm "away from my family".

You really have no idea how much it annoys me that the whole @#$#-ing country closes down just because of one religion's private issues.

Oh yeah, I'm at 34% now.

 

[blakerwry]

one downside to zip files seems to be their inability to get over 2GB using some zip rograms... the windows ME/XP zip integration comes to mind as well as some of the free zip programs i've tried.. I've never tried to make a >2GB zip archive using pkzip or winzip.

 

[blakerwry]

i use NTFS compression on my backup/bulk storage drive. it atleast effectively eliminates the excess space used by slack, most things on the drive are not compressable as they are already compressed archives/files.

 

[Jake the Dog]

RAR sucks Satan's ass. If the tools were anywhere near as usable, robust and well-integrated as ZIP, I might not have that opinion, but they aren't...

talk about being overdramatic :roll:

I compressed a folder containing various small images, binaries, ASCII and compressed CAB files totaling 353MB worth of 1,196 files in 107 folders.

using WinZip 8.1 maximum compression
size: 231MB
time: 292sec

using WinRar 3.2 best compression with recovery record:
size: 218MB
time: 383sec

results:
WinRAR = 6% smaller and that includes a data recovery record of about 2.2MB
Winzip = 24% faster

not a huge difference, but significant for huge archives I guess.

WinRAR does integrate somwehat into Windows. right-click menus are available in Explorer shells. RAR is a more robust format too. ever wondered why it's favoured by the more technically adept and serious warez groups?

I've never had a problem with WinRAR being unstable on any of the machines I use yet WinZip crashed after doing the test I ran above.

I don't mind zip as a compression format and WinZip as a tool but if I want to archive stuff I want to keep for a long time, I'll use WinRAR for it's parity methods, ensuring safe data recovery and as well, it's a better compressor.

 

[timwhit]

Also, RAR's are much better when using multiple parts. Which is also a necessity if you want to have recovery volumes available. RAR might be a little bit slower, but it is worth the extra time since I am only going to compress something one time.

 

[Mercutio]

Blah blah blah.

Is there some reason why I should have to wait hours to compress a few thousand files? Is that OK and normal?

'Cause that's what I'm seeing. On a fast computer. With gobs of RAM. That's not doing anything else except internet browsing.

 

[Howell]

I wonder if winrar is getting confused and trying to compress files that are essentially incompressable. These are jpegs right.

I also use NTFS compression on my personal drive. I so low maintenance. I have had zips become corrupted after moving them around.

AD, you might be able to get an additional level of compression by compacting your PSTs to clean out the chaff.

 

[Mercutio]

I ran it with the default options, but even if it is trying to compress JPGs, decompression shouldn't take hours.

 

[Fushigi]

Re:NTFS compression

If I compress a drive using, say, W2K, how portable is that compressed volumes? IOW if I compress an external USB2 drive can another PC running W2K or XP read/write the compressed volume?

Also, would a compressed volume created in XP be read/writeable by a W2K machine?

 

[Mercutio]

The only issue with compression is that the machine that receives the drive needs to support the same kind of NTFS (e.g. no NTFS5 on an NT4 machine).

 

[Jake the Dog]

normally I'd suggest you try a few other tests or another machine because obviously something is wrong with they way you've run your RAR test but ...

given how you so easily dismiss what's been said by timwhit and myself (with a lack of apparent testing on your behalf), it's obvious that there's no sense in talking to you about this Merc. I would have thought you'd give timwhit and myself at least a little consideration for what we have say.

we must have forgot that you are the man, you know better than anyone of course.

 

[Buck]

Whatever happened to Net Zip? I have the CD for that somewhere.