Robert LeBlanc wrote:
 > Bacula is very I/O intensive and right now that is not a very strong
 > point of virtualization.

This is not especially a problem with virtualisation per se, I suspect 
it is a problem generally with backing up. In a way virtualisation makes 
things worse as you can backup over memory (as that is now your network) 
so the disk i/o can be harder hit as a potential bottleneck gets removed.

We run Legato and backup terrabytes on ESX....about 12TB there seems no 
specific difference between physcial and virtual...(but thats 70TB physical)

We run almost entirely VMware ESX here. When
 > backing up 5 machines at once I've noticed very poor performance as
 > well. When we pulled the SD off of a VM and onto a physical machine it
 > helped out a ton.

Presumably no longer on the same disk sets? this can make a huge 
difference. I am concerned that Bacula is slower than I expected to 
backup, what I do intend to do is run some side by side tests Legato v 
Bacula and see what emerges.

 > VMware server is far worse when it comes to I/O.

Totally agree, man does it suck....

I run it at home with
 > Bacula and when you peg a VM with disk activity it just crawls.

Ditto any thing else that causes this.

The
 > other thing that you have to remember is that networking is all
 > virtualized and that creates a lot of overhead.

Cant say I agree here in terms of ESX anyway.

Since each machine has
 > its 'own' adapter, and to keep things isolated, TCP offloading can not
 > be used. That means the CPU has to do all the networking.

TCP offloading is not used by say Linux....you can get TOE based 
adapters, we have them on our Dells by default, and while MS can use 
them, does not seem to make much difference.

Generally these days with multiple Quad core CPUs, your memory runs out 
long before the CPU, eg in our Test&Dev we have 2 x quad 2.66Ghz core 
cpus with 24G Ram Dell 2900s they get to 50~60% memory usage while still 
on 5~14% CPU....so there is lots of CPU left...this is with 30~80 guests 
active across the pair....so there is lots of CPU left to move tcp 
packets. Add in Linux is generally regarded as a very efficient 
router/switcher/firewall engine.

 > VMs are really good at CPU and memory intensive workloads, disk and
 > network loads are getting better, but it requires the collaboration of
 > the hardware vendors to integrate virtualization into their products
 > like the CPUs.
 >
 > Robert

Our ESX servers have 4 x 4Gb Fibre connections into an EMC CX3-80 and 
the disk sets are R5(4+1) and 2xR5(4+1) this gives a lot of IOPS....we 
also fit 4/5 Quad port NICS and every connection is duplexed again 
giving us a lot of NIC i/o....but then we have 30 guests+ per Dell R900.

The hardest process on this setup is Legato without a doubt.

regards

Steven














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