[Samba] Mirrored samba servers.

[Nathan Vidican]

We're running a similar setup here actually, so a few notes that may be of
assistance to you are as follows:

#1 - RAID 0 + RAID 1 is poor for performance, if you want striping and
mirroring together you should probably be looking to some sort of parity
striping mode like RAID 5. We're using 3Ware Escalade 9000 series
controllers to do just that now with WDC 250GB Raid-Edition Serial ATA
drives now, and have been for quite some time. Performance is beyond our
expectations and reliability has been key.

#2 - Quit copying /etc/passwd, group, etc! Yuck... Try looking into
pam_ldap, nss_ldap, and samba/ldap configuration. OpenLDAP (free, open
sourced LDAP server), has replication services built right in, and can store
your users, passwords, mappings, and much more with full failover
capability. We're running FreeBSD/64bit, (on AMD Opteron machines), using a
primary/slave LDAP configuration wherein data changes are replicated
automagically using 'slurpd' - it was quite easy to setup and all the
necessary documentation exists on http://www.openldap.org/ - all of this
stuff comes 'standard' out of the box in the FreeBSD ports collection too :)

#3 - Along with your new LDAP-based database of users, passwords, groups,
mappings, etc, you might want to take a look at using some nice graphical
user management system - just simplify life for yourself if you're not
overly familiar with modifying entries in an LDAP tree - try LAM
(http://lam.sf.net/) - it's been great and I'm usuing it at several
installations now.

#4 - pam_ldap & nss_ldap (mentioned above) - will allow you to use the same
account information stored in the ldap database for BOTH unix and Windows
worlds - signle sign on is key :)

#5 - Setup samba for primary domain control, and setup the second machine
for secondary (BDC) services. We maintain the same shares on both machines,
and two dirs for login scripts; should the primary server fail for some
reason, the login scripts are over-written by the second set which maps all
the same drive letters over to the second server - not entirely transparent
mind you, but worst-case scenario if the main server goes out, is that users
logoff and back on and continue where they left off from half hour ago (data
replicated using rsync as well).

#6 - last advantage to this setup, involves a bit more complexity, but you
can device the load/shares out amongst the two servers and replicate
data/login scripts in both directions (as we're doing) - so your 'backup'
server is actually primary for some shares and vice-versa to the main
server, effectively distributing the load.

#7 - split your smb.conf files; keep one for PDC, one for BDC, and one for
all the shares that they replicate/share for each other - that way you can
rsync shares configuration file without changing the whole smb.conf file
(just use an 'include' line to include the shares from the main smb.conf's).

#8 - use CUPS; CUPS will replicate the printers across both servers and
allow for fail-over design as well... Still working on how 'transparent' we
can make this - so I won't feed you any details or bull about cause' I
really havn't tested it well yet.

All-in-all, not a pure 'High Availability' solution; but given a complete
catastrophic failure of our main/primary server, we can be back up and
running to within a half hour's data in less than a minute if need be -
fairly impressive, and definetly noteworthy.

Lot of food for thought, know this stuff can be overwhelming... Might send
an email back to the list with further details after you do some reading;
ie: what O/S you're using, LDAP/etc questions etc... Trust me, after having
done three of these setups now myself it's worth the effort. Good place to
start is the Samba Domain Control How-To, (which DOES explain
LDAP+samba+nss_ldap integration and provide example configuration files).

--
Nathan Vidican
nvidican at wmptl.com
Windsor Match Plate & Tool Ltd.
http://www.wmptl.com/


-----Original Message-----
From: samba-bounces+nvidican=wmptl.com at lists.samba.org
[mailto:samba-bounces+nvidican=wmptl.com at lists.samba.org] On Behalf Of
Richmond Dyes
Sent: Thursday, April 28, 2005 8:17 AM
To: samba at lists.samba.org
Subject: [Samba] Mirrored samba servers.


I have a customer that is using 250 gig drives for his business data.  I
have been using rsync to keep mirror copies of his data on a second
machine.  In the last 3 months I have lost 2 of four drives, the last
one being the system drive.  I have been doing a manual switchover. Each
time rsync runs, I copy my samba conf files, passwd, shadow and group
files from etc.  Has anyone setup a HA configuration for samba servers
on separate machines. If so, where can I get information for this kind
of setup?

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