Centos 5 + virtual machine + DNS?

[ranjitcool]

Hey Guys,

Would you guys recommend me having a DNS for my company on a centos5 VM?

Please advice, yes no may be why not?

RJ

[Rubberman]

If the VM is shut down because of whatever reason, then you are toast. Also, VM's do not perform as well as hardware-based systems, so you might find there is unacceptable latency introduced into the system. I would generally recommend a physical server to perform DNS server functions. FWIW, that could be one of the hosts for your VM's. With multiple cores (1 per VM plus at least 1 for physical host duties), the performance issue should not be nearly as severe. JMHO.

[HROAdmin26]

The OP never mentions what virtualization method is being used. But besides that, most of them are anything from 80-95% efficient - IE, the VM performance is only reduced by 5-20%.

Unless you are getting *thousands* of DNS requests a second, a DNS machine spends 99% of it's time idle - so now you have a VM that's sitting idle most of the time as well. Many companies have already virtualized large portions of their infrastructure - DNS is a prime candidate because they are typically low load servers.

For production DNS, keep in mind availability - there is no reason *not* to implement VM failover or primary/secondary DNS servers. Both the primary and secondary can be VM's, but make sure they're dependent on different HW. High availability is *easier* to implement in virtualized environments.

[Rubberman]

The OP never mentions what virtualization method is being used. But besides that, most of them are anything from 80-95% efficient - IE, the VM performance is only reduced by 5-20%.

Unless you are getting *thousands* of DNS requests a second, a DNS machine spends 99% of it's time idle - so now you have a VM that's sitting idle most of the time as well. Many companies have already virtualized large portions of their infrastructure - DNS is a prime candidate because they are typically low load servers.

For production DNS, keep in mind availability - there is no reason *not* to implement VM failover or primary/secondary DNS servers. Both the primary and secondary can be VM's, but make sure they're dependent on different HW. High availability is *easier* to implement in virtualized environments.

Excellent points! Another point to consider in such situations include the network traffic that the other VM's are generating/consuming on the host(s) where the DNS servers are located. Even if the DNS server itself is mostly idle, too much network traffic for the other VM's hosted on the same hardware can cause it to have excessive latency. I don't know if there are some VMM's that can prioritize traffic to/from particular VM's. That could be important in this case, and go a long way to eliminating that bottleneck.

[ranjitcool]

Thanks for the excellent replies guys,

Rubberman whats FWIW when you say ... "FWIW, that could be one of the hosts for your VM's"

Also I am using VMWARE.

I donno what HROAdmin26 meant by "The OP never mentions what virtualization
method is being used." whats OP? mean?

I realized that DNS is an idling server and I doubt if we are getting too many DNS requests.

I might also implement HA (high availibility and vmotion) so its available.
Another future ref point is that vmotion and other virtual machines use the dns vm for their dns needs, and if that dns is lost then these will be confused (coz they wont be able to find each other) so I was adviced by another techie to have the host names hardcoded in the hosts files of other vms. (how wud i do that if a vm was windows?)

RJ

[HROAdmin26]

OP = Original Poster = Person that started thread

FWIW = For what it's worth

Another future ref point is that vmotion and other virtual machines use the dns vm for their dns needs, and if that dns is lost then these will be confused

Then you don't have a highly-available configuration and have missed the point.

how wud i do that if a vm was windows?

Google/read a Windows guide and edit the Windows hosts file.

[Rubberman]

FWIW - For Whatever It's Worth
FYI - For Your Information
FIIN - Fark If I kNow! Sometimes can be FIIK.
ROFL - Rolling On the Floor Laughing!
RSN - Real Soon Now

I could go on, and on, and on...

[ranjitcool]

haha.. i knew 2 out of the 4 u listed, fyi and rofl ..

RJ

[ranjitcool]

I agree I was point out that the DNS needs to have a back up of sorts and thats where hosts kick in.

RJ

[HROAdmin26]

I agree I was point out that the DNS needs to have a back up of sorts and thats where hosts kick in.

RJ

No. A high-availability (HA) solution encompasses all possible failures. If you have an outage, then you have a flawed HA solution.

For production DNS, keep in mind availability - there is no reason *not* to implement VM failover or primary/secondary DNS servers. Both the primary and secondary can be VM's, but make sure they're dependent on different HW. High availability is *easier* to implement in virtualized environments.