Newsgroup: it.scienza.astronomia.seti
Titolo: L' originale !!!

etreff: SETI@home Server outage, attempted explaination...
  Datum: 13 Jul 2000 17:10:30 GMT
    Von: 
kor...@ellie.ssl.berkeley.edu
 (Eric J. Korpela)
  Firma: Cal Berkeley-- Space Sciences Lab
  Foren: alt.sci.seti, sci.astro.seti
We're probably going to be bringing the server back up in about 15
minutes or so.  I'll try to explain what happened and what it will
look like.
Because of the limitations of informix (2 GB chunks) and the limitations
of Solaris (on partitions per disk) we had been limited to using 9 Gb
drives for the science database, and were rapidly approaching the number
of disks our controllers could handle.  As a work around we were investigating
using Veritas to get by these limitations (which would allow us to use
18 Gb drives, in effect doubling our disk space).  
Before setting out to migrate the drives over to the new system we decided
performing tests to make sure it would work.  The information and advice
we had was to create a separate database space on the new drives, so a
failure wouldn't affect the existing database.  Well, it turns out one of
the tests did fail several days ago, but the database continued to operate
just fine, as was predicted.  Due to the failure the root chunk of the
new database space was corrupted.   This wasn't a problem until we restarted
the database machine to bring a new tape drive on-line.  After the reboot,
informix complained that it couldn't access the corrupted chunk and wouldn't
allow inserts into any database, including those unrelated to the missing
chunk.  We couldn't remove the bad chunk because it was corrupted,
Informix couldn't fix the bad chuck because it was too corrupted.  We couldn't
restore the bad chunk from a backup because no backup of the bad chunk
existed.  So we were stuck with a database that was readable, but not 
writeable.   
We eventually came to the concusion that the only way to get back up in
any reasonable amount of time was to restore the database to the new 18 Gb
disks using the last full backup (which took a bit more than 12 hours, we
should thank Matt and Jeff for getting up in the middle of the night to
change tapes). That's done, and we're getting to the point where we'll 
have enough usable work units to restart in a few minutes.
User stats shouldn't be affected, but science that are more recent than
the last full backup won't be in the new database.  It'll look like we've
gone backwards on the graphs page.  We've still got the missing science
on the old 9 Gb drives, but it'll take time and lots of informix tech support
to get it into the new database.
We've also got the problem that results will be coming back that don't
match workunits in the database.  I'm going to be stashing these until
I figure out what to do with them.  They'll probably have to sit on disk
until we get the database merged again.
Well, I'm off to start the server now.  
Eric
-- 
Eric Korpela                        |  An object at rest can never be
kor...@ssl.berkeley.edu
            |  stopped.
<a href="
http://sag-www.ssl.berkeley.edu/~korpela
">Click for home page.</a>

look like.
Bel casino e' successo.
Quello che non ho capito e' se effettivamente e' stato perso del
lavoro (e quindi verranno spedite unita' gia' analizzate) oppure dal
"merge" dei due database (quello vecchio solo "readable" e quello
nuovo) verra' ripristinata la situazione che c'era prima di questo
shortage.
Ciao
 Dimitri

 wrote in message
news:9l6smsotc75i3a0ht...@4ax.com...

Mi sembra di capire che una volta fatto il merging tutto dovrebbe essere a
posto, probabilmente ci saranno dei casini fino a che il merging non sara'
stato completato, cosa che potrebbe richiedere parecchio tempo.
Just my 2 cents!
--
Ciao
------------------------------
Antonio Gerli
f2...@mail.mdsnet.it
[sito] 
http://citylan.floating.net