Path: utzoo!mnetor!uunet!husc6!uwvax!oddjob!gargoyle!ihnp4!alberta!auvax!rwa
From: rwa@auvax.UUCP (Ross Alexander)
Newsgroups: comp.unix.wizards
Subject: Re: Hard linking vs. Soft linking on BSD
Message-ID: <466@auvax.UUCP>
Date: 22 Dec 87 01:11:03 GMT
References: <939DBLCU@CUNYVM> <6892@brl-smoke.ARPA>
Organization: Athabasca U., Alberta, Canada
Lines: 33
Summary: Yes, symlinks seem cheap enough in practise

In article <6892@brl-smoke.ARPA>, gwyn@brl-smoke.ARPA (Doug Gwyn ) writes:
> In article <939DBLCU@CUNYVM> DBLCU@CUNYVM.CUNY.EDU writes:
> >I have a follow up question on using soft links. Is there a pronounced
> >performance cost by using such a link, or is it negligible?
> I have trouble imagining an application where the cost would be
> noticeably more than some other approach that accomplishes the same
> thing.  (I phrased this strangely, to acknowledge that the target
> of a symlink might be a remote file system, for example.)

One of our machines here (auvax) used to have 3 ra81's, which had
three user-account filesystems named (strangely enough) /usr[123].
This worked quite nicely until the day came when I had to pull a
drive offline to test a new (and subsequently discovered, extremely
bug-prone) version of Ultrix.  This was forced on me by a change in
the size of the inodes, but I digress.  

Now my user community, in their infinite wisdom, had scads of code
containing pathnames of the form '/usr1/twit/bar/foo', et c., et c.,
(despite considerable flaming on my part well before this problem
arose).  Said pathnames being hardwired in, and not a few of 'em,
either, I really was puzzled for a while, at least several minutes,
as to how I could fake this thing without breaking every
user-designed programme in sight.  So I ended up repartitioning the
two remaining 'public' drives with /usr[ab] partitionas, with
/usr{1,3} being mapped into /usrb via symlinks in /, and /usr{,2}
mapped into /usra ditto.  

The upshot of this is almost every path in the system now has a symlink
in it.  Performance has not noticeably altered.  So much for the
symlink penalty ;-)

Ross Alexander @ Athabasca University,
alberta!auvax!rwa