> ** Reply to note from yngvar.folling@login.eunet.no Mon, 15
> Dec 1997 02:09:50 +0100 (MET)
Maybe I should make it clear that I have not seen the code for Yarn.
All I know about its behaviour is what I've observed for the three years
I've been using it -- and some comments I've seen here before.
> Question: When I run rmgroup, does this work like expire, i.e.
> it is only freeing space WITHIN news.dat and not shrinking its
> size?
This was in fact something I meant to ask. It seems clear that rmgroup,
like expire, cannot move articles within the file, so it can only delete
whatever space happens to be freed at the end of the file.
However, I don't know exactly at what point the space taken up by the
articles of those groups is made available again for new imports. The
rmgroup command itself runs quite quickly, which does not seem to fit
the idea that it does some of the same operation as the slow expire.
On the other hand, expire only counts up the articles in the remaining
existing groups. I sure *hope* that it still reclaims space from the
deleted groups as well, or the articles will permanently take up space.
This doesn't seem to happen, though.
Digression: I remember that when Yarn organized its newsbase in a group
of files according to their expiration dates, the articles of removed
groups weren't actually deleted until their normal expiration time came.
I tended to run "Catchup" on them all and then run expire -r before
actually removing them.
> All in all, isn't there a point when you HAVE to run rebuild
> -s on news.dat because the proportion of small chunks of free
> space that will only very unlikely ever be overwritten/reused
> will rise continuously? Like fragmentation on FAT drives?
Well, assuming that your usual amount of news stays constant, you will
always have about n articles in the file. You can then only have a
maximum of n areas of free space in the file as well. (I almost said
n-1, until I realized that there *can* be free space at the very
beginning of the file, too.) The only thing that can make the file grow
after that, will be if the average size of each space kept increasing,
but obviously, at some point the individual spaces get large enough to
import new articles into. So I expect there to be a limit.
Hmm. Something occurred to me. If two adjacent articles both are
deleted, I sure hope that their space is consolidated into a single area
of free space, and not two.
Anyway, I *have* run rebuild -s for its intended purpose. I had some
corruption of the newsbase only last week. Before I did that, however,
I ran expire -r. I lost most threads, and as I said, the articles were
in a completely wrong order.
Bizarre corruption, though. I had run a quite normal import, and had
some of my mail filtered into pseudo-newsgroups. When I entered one of
those pseudo-newsgroups, though, I got a red box message saying
something like "Couldn't find article xxxx." But xxxx was *not* a
Message-ID, but some text from *another* mail that had *not* been
filtered.
I've got expiration times on various newsgroups ranging from three to 30
days. Slightly distressed to see that the current last article in
news.dat is an article in one of the 30-day groups -- that I imported
yesterday.
Yngvar