Network slows down sporadically

What speed are the switches your running on?

Don't suppose there is a backup running at the time of the slowdown lets say for EG an online backup?

What do you use for a backup does it backup out onto the cloud?

Can you give more information on grinds to a halt? are internal ping responses slow? external ping responses slow?
What are your main symptoms here for grinding to a halt?

What i have noticed  is crashplan pro running on a couple of servers....

Sounds like a network bottleneck seen this before when guys had 100MB switches on a network and the switches are basically being flooded causing a bottleneck.

What speed make and model are the switches used here how many of them too. Any other info is helpful.

Crashplan pro is a online backup tool :o good guess. Id start looking at this. Can it not be run out of hours?
How much data is it backing up too?

Netgear Gygabytes PRO 4 switches-
1.5 Terrabyte being backed up- supposedly overnight- but it remains running during the day for some reason....

Wow that's one hell of a backup so there 1GB switches right?

Are you guys running a full backup every night? If so that's the issue and this has to be changed, run a seed backup and then configure the software to run incremental/differential based on your needs after that. If it were running a full backup everynight it could easily run into the next day.

With a backup that large 1.5TB cant be running that as a full everynight on these switches.
Can you state the backup schedule?

If I were you I may add id contact crashplan pro support on this and ask them to advise about a recmonded schedule and configuration or whoever it is that regularly configures this software for you.

So i went into the dashboard of crashplan and it was set to run every 15 minutes at 80% of CPU - i reset it to run every 12 hours to see if that makes a difference- because it is running on the PDC - or DNS server- this may cause the users to experience lag on the Network? but,, why would the phone system also lagg ? it is a Linux box running Fonality...

If its running every 15 minutes and through the same switches and firewall and constantly backing up 1.5TB id expect to see something like that.

Sounds like you need a new backup schedule, do you have support for this product?
If so ill let my contribution end here. I am more than happy to help if you do not have support.

Maybe you should consider separating your phone network, add a second lan zone on your firewall onto a different subnet and reconfigure the phones to work from there. That will sort that one out.
Sounds like things are not setup too well there tbh no offence.

Will do that- company has grown- set up was good for a while- servers added, phones, network printers- the problem with the second subnet is the HUD interface for the phones on the PC's....

Thanks !