after sold 30 VPS with KVM, I found, KVM's memory can also be oversold

lewissue

in a 32GB Dedicated Server, I can oversell 30x1.5GB

but my Chinese friends always tell me KVM has no oversell

WHY?

ATHK

Sigh...

cppgohan

http://docs.fedoraproject.org/en-US/Fedora/13/html/Virtualization_Guide/sect-Virtualization-Tips_and_tricks-Overcommitting_with_KVM.html

It is possible to run with an overcommit ratio of ten times the number of virtualized guests over the amount of physical RAM in the system. This only works with certain application loads (for example desktop virtualization with under 100% usage). Setting overcommit ratios is not a hard formula, you must test and customize the ratio for your environment.

also this one:

http://www.linux-kvm.org/wiki/images/f/ff/2011-forum-memory-overcommit.pdf

Silvenga

You do know that KSM was made by the KVM devs?

Chuck

If you get your customers mad, they will leave you. End of story.

lewissue

@cppgohan said:
http://docs.fedoraproject.org/en-US/Fedora/13/html/Virtualization_Guide/sect-Virtualization-Tips_and_tricks-Overcommitting_with_KVM.html

http://www.linux-kvm.org/wiki/images/f/ff/2011-forum-memory-overcommit.pdf

I see~ Thanks for documentation

@Chuck said:
If you get your customers mad, they will leave you. End of story.

I'm not mad, so I'm not overselling them for my customers, I'm just testing :P

rds100

said: in a 32GB Dedicated Server, I can oversell 30x1.5GB

Shhht, don't tell anyone!

tarasis

Ah, is that why a number of offers says XXXX dedicated RAM, and xxx burstable RAM

netrix

@tarasis said:
Ah, is that why a number of offers says XXXX dedicated RAM, and xxx burstable RAM

i think it's only on OpenVZ

coolice

I always wonder why people think you can only oversell OpenVZ... All virtualizations are made with over committing capabilities to effectively utilize corporate resources...

ndlong75

i am new, thanks for the infos

cnbeining

That was an ancient post on Chinese forums, which gives the false information.

But most people would repost without any thinking. That's the reason that this rumour still lasts...

DalekOfSkaro

coolice said: I always wonder why people think you can only oversell OpenVZ... All virtualizations are made with over committing capabilities to effectively utilize corporate resources...

AFAIK, you can't oversell VMWare.

coolice

VMWare it is bulid for that

thin provision, vcpu, memory compresion, memory baloning.... it got it all (other hypervisors do not have memory compression) table1

https://labs.vmware.com/vmtj/memory-overcommitment-in-the-esx-server

Memory overcommitment in ESX is reliable (see Table 1). This implies that VMs will not be prematurely terminated or suspended owing to memory overcommitment. Memory overcommitment in ESX is theoretically limited by the overhead memory of ESX. ESX guarantees reliability of operation under all levels of overcommitment.

When ESX is memory overcommitted, it allocates memory to those powered-on VMs that need it most and will perform better with more memory. At the same time, ESX reclaims memory from those VMs which are not actively using it. Memory reclamation is therefore an integral component of memory overcommitment. ESX uses different memory reclamation techniques to reclaim memory from VMs. The memory reclamation techniques are transparent page sharing, memory ballooning, memory compression, and memory swapping.

Shoaib_A

@DalekOfSkaro said:
AFAIK, you can't oversell VMWare.

VMware supports disk & memory overselling both.

DalekOfSkaro

K2Bytes said: VMware supports disk & memory overselling both.

Disk overselling can happen only if you thin-provision. If you thick-provision your disks, you can't oversell. As for Memory, it may be true to a point.

socials

@DalekOfSkaro said:
Disk overselling can happen only if you thin-provision. If you thick-provision your disks, you can't oversell.

That's like saying "You can move faster if you run. If you don't run, you don't move faster". Like.. no shit.

And yes, you can overcommit in VMware every way you want.