Tom Lane skrev:
But a virtualization layer can kill your performance and/or
reliability. Ask hard questions about why that decision is being
imposed on you and what benefits it will have.
I have been following this discussion, and I feel I have to make a comment.
Our company has moved all servers to a fully virtualized environment
(VMware).
Instead of having to deal with a bunch of physical servers we now have a
clean setup with two 'irons' running vmware, and a pack of disks (SAN).
If any of the disks should fail, we can simply exchange it without
disturbing the running servers.
If one of the physical machines have some trouble it automatically
switches to the other one, again without disturbing the running servers.
If we wish, we can move a running PosgreSQL server from one physical
machine to another without stopping it or disconnecting users.
- Want more RAM? Adjust the value on the virtual machine.
- Want another CPU? Just add one.
- If I need another PostgreSQL server I just ask for a clone and it is
ready in 10 minutes. You can even clone a running server, data and all.
If I need the server for testing I can download a clone to my own
computer and run it there under VMware Workstation or Player.
I can make a new virtual machine on my own PC and when I am done setting
it up I give it to the IT guys and they start it on the big irons.
This setup is extremely flexible and saves A LOT of work. It also has a
huge impact on the reliability and performance. The performance of the
virtual servers are awesome.
BTW: we are running PostgreSQL 8.3 and 8.4 servers on Ubuntu linux on
the virtual machines.
On my own development computer I am also running virtual machines; one
running development tools, another a PostgreSQL server, a Windows
machine running some client application using the database server etc.
I will prefer a virtualized environment over physical machines any time.
Regarding performance, on my development machine (a Lenovo ThinkPad
W700) the virtual PC's are running at about 90-95% of the speed on the
same hardware without virtualization.
Regarding 'pulling the plug' on the servers: Physical or virtual, always
use a UPS. You can pull the plug as much as you like. When the power is
about to run out it signals the server, which shuts down cleanly.
Our servers have dual powersupplies, connected to separate UPS'es on
separate power sources...
In a nutshell, I am heartly recommending virtualization.
And - I do not want to start a discussion about it. Just sharing my opinion.
/Jan-Ivar
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