[K12OSN] Adding another server as backup.

Martin Woolley sysadmin at handsworth.bham.sch.uk
Wed May 11 13:32:26 UTC 2005

On Wednesday 11 May 2005 09:02, Sudev Barar wrote:

> How is the home directory served? By a different backbone on all
> servers?

Some via NIS/NFS some via Samba depending on the how long the student has been 
with us.  For NIS, I've scattered the home directories evenly amongst the 
servers and each server has the /home directory of all the others mounted via 
NFS.  Each server has a directory under /home which corresponds to each of 
the servers, thus we have /home/LISA, /home/BART, /home/MARGE, etc.

Here is a 'df' for lisa
 /dev/hda3              3526204    214412   3132668   7% /usr/local     59717280  10127936  46555872  18% /home/HOMER     59717280   8552608  48131200  16% /home/MARGE     59717280   8435520  48248288  15% /home/BART    100932544   8421824  87383584   9% /home/MRBURNS    59661024   4569632  52060736   9% /home/MAGGIE

See how all of the /home directories for each of the other servers are mounted 
on 'lisa'.  A similar configuration is in place on the other servers.  Now on 
'lisa' the /home/LISA directory contains a bunch on sym links to the home 
dirs that reside on lisa and similarly on the other servers.

# ls -ld /home/LISA
lrwxrwxrwx   1 root    root       13 Nov  2  2004 adnam04 -> /home/adnam04
lrwxrwxrwx   1 root    root       13 Dec  8 13:37 alhog03 -> /home/alhog03
lrwxrwxrwx   1 root    root       13 Nov  2  2004 alixm04 -> /home/alixm04
lrwxrwxrwx   1 root    root       13 Nov  2  2004 almua04 -> /home/almua04

The final bit of the jigsaw is the password file.  The YP server runs on lisa 
so each user is authenticated by that box.
# tail /etc/passwd
sanda04:x:720:100:Sandhu Aaron:/home/MAGGIE/sanda04:/bin/bash
shara04:x:721:100:Sharif Aadam:/home/MRBURNS/shara04:/bin/bash
sharp04:x:722:100:Sharma Pavan:/home/LISA/sharp04:/bin/bash
verma04:x:723:100:Verma Akshay:/home/MARGE/verma04:/bin/bash
shahi99:x:724:100:Shahan Imran:/home/LISA/shahi99:/bin/bash

Notice that the home dirs are scattered across the servers.  Thus no matter 
which host provides the user with a login, their home dir is still 

> Very interesting......Did I hear a collective gasp of all the load-
> balancing scripting guys?

I doubt it; our solution is not the most elegant and there are no doubt huge 
bottlenecks in the works.  Access times are acceptable but not brilliant.  
Most of the students use the IT suites for web surfing (and playing games on 
the internet).  I don't really care how slow their internet access is.  Word 
processing (the other big load) is usable once the document is loaded.  What 
I'd really like to see is a multi-processor setup and a huge raid farm for 
the home dirs; something like the Beowulf cluster might do the job.  We have 
aquired an IBM RS/6000 SP/2 which will do exactly what I want.  Now if only I 
can find the time to set the beasty up.
Martin Woolley
ICT Support
Handsworth Grammar School
Isis Astarte Diana Hecate Demeter Kali Inanna

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