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I've been lurking here for a while, and I think I've got almost enough
info to do this HA-LVS thing. But I thought before I delve into this,
I would submit my proposed design to the list and your combined wisdom.
Situation: Small College with mostly Linux infrastructure, wanting to
increase reliability and scalability. Currently about 2500 active email
users, 300 active SMB file sharers
Current design: a couple dozen Linux + AIX + WinNT + Win2K boxes, some
dedicated and others multi-service. RAID5 on the mail and samba servers.
http servers all over the place.
Proposal: an LVS-DR system including at least 4 RealServers to handle
ftp/http/ssh/??? (whatever we can do) The Director would have an HA
silent failover (pulse?) There would be separate servers for SQL, Mail,
SMB/NT Auth (Samba), DHCP and LDAP. Each of these servers would be in
the HA mode, perhaps sharing a RAID5 arrangement along the lines of the
article by Blackmon & Nguyen in Sysadmin, Sept 2001.
All Realservers would obtain their static data from a NAS device
(SnapAppliance 4000?) via NFS. The NASes would be rsynced by the DHCP
server when it wasn't handing out IP numbers (boring job... but someone's
got to do it).
LDAP would be the authentication method for all systems.
See
http://pulsar.westmont.edu/academic_computing/presentations/lvs2001/proposed.dia
for a 'dia' diagram of the proposal,
(or
http://pulsar.westmont.edu/academic_computing/presentations/lvs2001/proposed.ps
for postscript)
Questions:
Realistic ?
DR vs. NAT? (The Linux Journal article in April indicated NAT was limited to
about 1700 tps... we don't approach that volume, but it also looked like DR was
cleaner. No?)
Can any other services be accommodated by the LVS - e.g.
DHCP,
LDAP,
DNS,
IMAP,
SMB
What big piles of poo do I need to avoid stepping in?
What would you estimate for amount of time to implement something like
this? (i.e., 4 LVS RS's, 6 HA servers? - assuming that the setting up
of the service itself has already been done)
Bottlenecks?
Where do you need power & memory hungry monsters for servers, and where
can you do just fine with low-end (e.g. 300MHz Celeron) computers?
Is it realistic to have the Directors have no hard drive, but boot off a
floppy with Linux Router Project images? Boot off a CDROM image?
I see the Directors usually have 2 ethernet cards... Where else would
multiple cards be highly desirable?
My earlier question about SMB was greeted with "you'll be the first"... is
there a technical reason why SMB wouldn't be possible with the LVS, or is
there an outside chance my effort could be rewarded? I'm not terribly
interested in lost causes.
Thanks, all, for any input on these questions.
John
John Rodkey
Asst. Dir. of IT, Westmont College
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John Rodkey, Information Technology, Westmont College
rodkey@xxxxxxxxxxxx
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