Clearcase vs. CVS?

briany asks: "I have been asked to evaluate Clearcase vs. CVS. I am wondering what kind of experiences people have had (good and bad) with either product, or if there are other products that should be considered. The projects that will be stored are rather large (10+ GB) and need to be accessible from Solaris, Linux, and NT/Win2k." Of course, it should be mentioned that Clearcase is available for Linux, as well as other unix clones.

Comments

A rather sketchy testimonial

[A nonymous Coward]

I've used CVS a lot, but never in big projects. I was told I had to use clearcase once, and the sysadmin botched the install so bad I dumped it and they backed off when I threatened to quit. (I was on a separate project with only a few programmers who were all happy with CVS, so the rest of the dev staff could use punched cards and it wouldn't have bothered us.)

For what it's worth, I understand one big difference is that clearcase automates things like tracking the compiler and lib versions, so you could go back a long long ways to reproduce a really old version byte for byte. Another difference is that it eliminates dup copies of source and object files among the staff, potentially saving space and time. How well this works in practice, I don't know, and I've never felt any need for it.

The other comment about needing more sysadmin work is certainly true. In addition to the loon who clobbered my system with the bad install (Sun OS, early 90s), a different sysadmin, purportedly her boss, twice erased the entire clearcase repository. Apparently it was too tricky for the average bear. I see that as two strikes against clearcase just from the point of not being very maintainable, and hope to never see it again.

CVS is good. Text files you can edit in an emergency or just in readonly mode to see when things happened, as opposed to SCCS, and it is just plain good. Be happy with CVS. Your repository is valuable -- don't give up control.

--

pro ClearCase

[The Pim]

I'm surprised there are so few supporters of Clearcase here. Yes, it has two primary disadvantages: it is big, expensive, slow, bulky, and administor-intensive (I'm only counting that as one :-) ); and the repository is binary and opaque, accessible only via Clearcase commands.

But it is so much more elegant than CVS if your use of version control is at all sophisticated! (Which, if your development effort is even medium size, I would argue it should be--this is stuff that pays off. But that is a separate discussion.)

For starters, there are some simple correctness issues. Clearcase tracks files across renames, which I gather CVS does not. Moreover, it versions directories, so if you look at an old view of the repository, you see the old names. This allows everything from corrections to badly chosen filenames, up to reorganization of the repository, without any fuss.

Clearcase also has a "findmerge" command with "common ancestor" support. This basically means, when it's time to merge, you always know exactly what you need to merge, with previous merges taken into account. I honestly don't know how you could live without this. (Note this is distinct the tool that actually performs merges, which is nothing special--I just use GNU diff3, myself.)

Second, clearcase has (to me) a killer feature, filesystem support. This means that that you get an ordinary-looking unix filesystem that automatically gives you the latest versions that you're interested in. Further, using an "extended" filename syntax, you can look at any version right from the filesystem. So if you want to see what's going on in the foo branch, you just vim code.c@@/main/foo/LATEST, or if you want to figure out which mainline versions use the fooble API, grep fooble code.c@@/main/*. This is addictive. NB: the filesystem support is not available in Linux :-(

Third, clearcase is very unix-friendly. While this is not a major difference with CVS, it is still worth pointing out (since many commercial products "don't get" unix). Most clearcase commands are close to their unix analogs (or in the same spirit, when there is no analog), and the documentation is in man pages. For me, this made learning clearcase easy, and adds a significant comfort factor.

To me, version control is not just about making sure I can work on my stuff without getting stepped on by anyone else. (CVS is fine for that.) It's also about expressing, understanding and managing the relationships between various versions and branches. This is a conceptually more difficult activity, and I frankly think many posters here don't see its value (it takes a while). But if you do, clearcase wins hands-down.

I admit that, while I have used CVS, I have only had day-to-day experience with clearcase (and Visual SourceSafe--bleh!), so I don't have a good sense of the "CVS routine". It perhaps includes some practices that mitigate the lacks I've cited. But, as long as someone else is taking care of the cost and administration and resources (under these circumstances, I have found clearcase reliable, if still a bit pokey), and I don't have to interoperate with outside developers who don't have clearcase, I would take clearcase in a second.