Alzheimer's Syndrome (a.k.a. disappearing inodes) analysis & test

[Peter Jeremy]

In article <1384 at cooper.cooper.EDU> mayer at cooper.cooper.EDU (Mayer Ilovitz ) writes:
>	Because of all the postings which have appeared over the last few weeks
>in various newsgroups concerning mysteriously disappearing inodes
>which reappear after performing an fsck on the afflicted file system,
>I am reposting this article which will (hopefully) answer many of the
>questions. ( this was originally posted the week of Thanksgiving Day 1987.)
>
>Since the original posting, I have heard a rumor that the inode allocation/
>free bug which is responsible for these problems will be fixed in System V 4.0.

Just out of interest (I hadn't seen the problem, but I don't run any
filesystems close to inode capacity so I mightn't), I tried the procedure
on XENIX/286 2.2.1, and to my surprise, it passed the test.  At step 15,
it allocated inode 32 (I kept going and it happily allocated 33..39 and 202).

It looks like this is one bug that Microsoft or SCO corrected.  One
interesting oddity was that when using the inodes initially (on a
filesystem that has just been mkfs'd), it allocated 3..202, 211..272,
203..210.  There was also a noticable delay between allocating 202 and
211, although this may just have been the system load (I was using a
floppy disk for the experiment).  This doesn't quite jell with my
understanding of the way inode allocation is supposed to work (on a
clean file system the free inode list should be sorted, and therefore
inodes should be allocated in inode order).
-- 
Peter Jeremy (VK2PJ)         peter at stca77.stc.oz
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