Tim Churches wrote:
Duncan Guy wrote:
In total we have 7 servers doing different jobs, would be good to get
them all working on the same team or outsource it totally,
I think there's a lot to be said for running seven servers to do seven
different jobs.
Running as virtual servers on fewer machines is unlikely to improve
performance - the main advantages are reduced hardware, hotel (power,
aircon, rack space), system admin and back-up costs. The downside is
reduced hardware redundancy - if the host machine fails, all your
virtual servers have failed too, so a hot or warm spare server is pretty
much essential.
I think there's a lot more to be said for running seven virtual servers
to do seven different jobs.
We have one server that dishes out virtual machine kernels, does web /
mail hosting, DNS, samba shares / PDC, jabber serving and probably a few
other things I've forgotten. It's a low end Celeron that I build for
about $450. Apart from the occasional rsync burst most of the time CPU
use sits at 0.3%. However, since we added mail processing to elimate
spam, it's shot up to about 2 to 5% running over 20 checks on every mail
we get, which is about one every six seconds.
It's amazing how little you need with headless linux.
DRBD (http://en.wikipedia.org/wiki/DRBD) is the hot, new, groovy way to
do failover under xen (http://xenamo.sourceforge.net/). I might get
around to that before the end of the year.
I always caution people that RAID and failover is *NOT* backup. I have
experienced widespread filesystem corruption mirrored with 100% accuracy
onto to the other discs in the RAID. Cold, regularly tested replacement
servers are still necessary for mission critical apps.
However, dual-quad-core servers (so that is eight 3GHz CPUs in one
server) are now only about $15-18k with 8GB or RAM and some RAIDed
discs, so it may be possible to consolidate a lot of those servers onto
one machine. It may be that inter-server network bandwidth/latency is
the problem, in which case consolidating on a multi-CPU machine may
help.
I went low end since I am but a poor country general practitioner.
Intel Server Board S5000PSLSATA motherboard
Intel Entry Server Chassis SC5299DP
8GB 4x2GB Kingston KVR667D2D4F5/2GI RAM
Samsung SATA DVDRW
2 X E5320 1.8GHz
Total $4331
The good news is that Intel's dropping (?dropped) the price for Duo
Cores this month so a backup machine should be under a grand.
You need someone who knows what they are doing to diagnose your
performance bottlenecks (by instrumenting your network and servers,
capturing data, and then analysing it - not just giving the usual
seat-of-the-pants "add another server" opinion).
I really think there's a lot to be said for getting expert opinion in
this area. (I haven't.) The real fear for us will be bottlenecks in SQL
server performance. I am planning to put our database on a single
processor with 4 gig of RAM that should go close to keeping the entire
database in memory. Suck it and see I guess.
If you have 7 sites, then having your servers hosted in a big data
centre may not be a bad idea, though.
Duncan, virtual servers are the next big thing in computing allowing
significant economies of scale. (Factor of ten I am guessing.) If your
data is mostly off the LAN the data centre may be your best bet. There
are lots of options out there and prices can vary from $5 to $3000 per
month depending on what you need and want.
Cheers.
David
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