How much memory and swap space I should have for VM Hosts

[MJA_1]

How much memory and swap space I should have for HP-UX VM Hosts if RX6600 have 48 GB Ram and going to build 2 Guests with 24GB in it (according to client requirment).
I knew from this forum I should have at least given 8 GB memory to VM Hosts and 20gb and 20gb memory should give to guests.My question is that 8GB memory for VM Hosts will be good enough or I should give more for better performance. And if I am going to give 8 GB to VM host and 20 gb to both Guests then how much swap space should be in HP-UX VM Host,

Thanks .. MJ

[Tim Nelson]

You really, really, really need to start here.
http://docs.hp.com/en/oshpux11iv2.html#HP%20Integrity%20Virtual%20Machines

Without having some basic understanding you are not going to get anywhere.

8GB RAM for host is great
Need at least 28GB swap ( 24+4 as stated in the IVM manual)

>>And if I am going to give 8 GB to VM host and 20 gb to both Guests then how much swap space should be in HP-UX VM Host,

The last sentence does not make sense. If you mean swap space in VGuests, then apply your basic UNIX adminstrative skills. I would recommend a minimum of 12GB of swap in each VGuest, if you think you need more because you plan on swapping then I have no advice for you.

[Michael Steele_2]

I just had a HPVM course in this, for SWAP surprisingly, its 1.5 times RAM.

page 16 of below link:

1.5 times physical memory for swap space (for example, for 1 GB of RAM, swap
space should be 1.5 GB)

For RAM its application dependent:

page 26 of below link:

System Requirements
Table 3â 1 describes the minimum configuration requirements for installing Integrity VM on the VM Host
system.
Table 3-1 Requirements for Installing Integrity VM
Required Resource Description
Computer An Integrity server
HP-UX 11i v2 May 2005 or later, running on an Integrity hardware platform, as well
as any appropriate software patches. The license for Integrity VM includes the license
for running the HP-UX Foundation Operating Environment on the VM Host system.
Operating system
Local Area Network (LAN) card Required for network connection and configuration
Source installation media An appropriate source for installing software (DVD or network connection).
Disk storage Sufficient disk space for the following:
â ¢ The VM Host operating system (refer to the HP-UX 11i v2 Installation and Upgrade
Guide)
â ¢ The VM Host software (50 MB)
â ¢ 1.5 times physical memory for swap space (for example, for 1 GB of RAM, swap
space should be 1.5 GB)
â ¢ Disk space for each guest operating system, including swap space
â ¢ Disk space for the applications running on each guest
Memory Sufficient physical memory (RAM), including the following:
â ¢ 750 MB + 7.5% of additional memory
â ¢ Memory required for each guest (operating system and application requirements)
(HP-UX 11i v2 May 2005 requires a minimum of 1 GB of memory, so a guest
running HP-UX must be configured with at least that much memory.)
â ¢ Additional 7% of guest memory for overhead
To determine the total memory required for your guests, refer to â Planning Your Virtual
Machines,â in Chapter 2.
For example, for a VM Host with 16 GB of memory, the memory requirements would
be calculated as follows:
â ¢ 2.1 GB for the VM Host (16 GB minus 750 MB)
â ¢ 3 GB for an HP-UX guest (guest requires 2 GB, plus 1 GB operating system minimum)
â ¢ 3.21 GB total guest requirement (3 GB + 7%)
â ¢ 10.69 GB remaining for additional guests (16 GB â 2.1 GB â 3.21 GB = 10.69
GB)
The software bundle T2767AC. Refer to â Bundle Namesâ for information about the
required software for installing Integrity VM.
Integrity VM software
A configured and operational network, with at least one LAN card if you plan to allow
remote access to guest virtual consoles. To allow guests network access, the VM Host
must have at least one functioning network interface card (NIC).
Network configuration

http://www.docs.hp.com/en/T2767-90004/T2767-90004.pdf

[Hein van den Heuvel]

Why you you think you need 8GB for the Host?
What is it supposed to do with all that?
It's just an empty shell!
You do have to give it a fair bit though.

According to "HP Integrity Virtual Machines
Installation, Configuration, and
Administration Version A.03.50"

Table 2-1 Requirements for Installing Integrity VM (continued)

--> 750 MB + 7.5% of memory beyond the first GB
That would be a 3.525 GB. Not too shaby, but not 8GB either.

See: http://docs.hp.com/en/T2767-90105/T2767-90105.pdf

fwiw,
Hein.

[Hein van den Heuvel]

Argh, sorry for repeating most of Michael's reply.

And what's worse, I think I got it wrong....

There the bullet: "Additional 7% of aggregate guest memory for....

So that's really almost 15% give or take.
And that does indeed bring you close to 8GB.
Yikes.

Hein.

[Eric SAUBIGNAC]

Re-Bonjour MJ,

Many things already said. So, just some comments :

+ First be very, very careful with memory.

With 48 Gb of memory, and according to the rules defined in the configuration guide, if you suppose that the host will claim only 1 Gb (that is without a safety belt - discussed later in his post), you can allocate only a total of 41 605.98 Mo to the VM. That's a fact. Can you do that ? No you can't.

Because you can sometimes ask for more than 1 Go on the host or have memory fragmentation. For example you can connect to the SMH, you can have an ignite process that start, stop one VM, doing something else on the host ... then there is no guarantee that you will be able to start the VM again. So you must have some free memory on the host to prevent that.

So what is the right way to calculate memory needs. I have the following rule :

- How many memory I want to give to all of the guests ? In your case 24 + 24 = 48Go = 49 152.00 Mo
- How many memory do I need for this : 49 152.00 Mo * 1,07 = 52 592,64 Mo
- How many memory will I need on the host to manage this need : 52 592,64 Mo * 7.5% / 92.5 % = 4 264.27 Mo
- So it means that I need 52 592,64 Mo + 4 264,27 Mo = 56 856,91 Mo to allocate 48 Go RAM to the VM
- How much for the host OS ? I tend to say 1 Go would be sufficient but I want a safety belt, so I guess I need 4 Go that is 4048 Mo.

>>> Total : you need 60 904.91 Mo as physical memory

Now take it in the other side as described in the configuration guide :

- I said 4048 Mo (safety belt !) for the OS Host.
- So free memory is 60 904.91 Mo - 4 048 Mo = 56 856.91 Mo
- So, for the VM Host I need to add 7.5% of 56 856.91 Mo, that is 4 264.27 Mo
>>> Total for the host 8 312.27 Mo = 4 048 Mo + 4 264.27 Mo
- Guest requirement : 48 Go (49 152 Mo)
>>> Total Guest requirement 52 592.64 Mo = 49 152 Mo * 1,07

>>> Total physical RAM : 60 904.91 Mo = 8 321.27 Mo + 52 592.64 Mo

In a conclusion you must calculate very, very exactly how much RAM you need and you MUST ADD A SAFETY BELT. The more RAM, the better it is. Some say that if you want to allocate X Go to the guest, then give 2X Go to the host. IMHO I think it is too much, but if you want a fast compute take a ratio of 1.5

+ You said : <8 GB memory to VM Hosts and 20gb and 20gb memory >

According to previous comment (safety belt again !) 40 Gb allocated to Guest needs a system configured with 51 428.76 Mo of RAM. You have less. With 48 Go, and if you consider my "safety belt" (that is the 8 Go you spoke of for the system ?) I guess you can allocate only 37 Go to both VM.

+ You said

Your VM Host is not supposed to swap. A VM is loaded only if there is sufficient memory to keep it in RAM. So you must do what is needed to reach this goal : add more RAM or reduce VM Guest RAM allocation.

+ You said

The swap is calculated based on physical RAM. In a VM Host, pseudo swap is deactivated. So if you want to be able to use all of the memory you must have at least the same swap size as RAM. And as you are not supposed to swap just add 4Go to the RAM size. 1.5 x RAM as swap size was a recommendation from version 2 and below. Of course, if you can afford it, you can have a 1.5 x RAM as swap size but there is no need for that. You must not swap on the host, unsless you use in a mindless way some applications on the host.

And as usually ... please be fait with my english !

Regards

Eric