low I/O performance after getting the VM more than 2048 GB RAM (VMware Server)

[mfgoenk]

Hi all,

sorry i don`t know if it has ben asked bevor but i did not find this question in the forum. I have the following problem:

I have an VM with the following configuration:

• First hdd is a virtuall one with 50 gb splitted into 2 GB files

• Second and 3 hdd is an iscs lun on a san.

When i give the vm an amount of ram between 384 and 2048 mb ram it has great performance. i/o is about 600 mb/s on the vm hdd and stabel about 50 mb/s on the iscsi hdd`s.

Now i want to install oracle on the vm and my oracle guys told me the want sa much ram as possible.

I thought no prob and gave the vm 3600 mb ram. After rebooting the complete host with all of his vm`s gets very slow. I found out that i the i/O gets down on the vm from 600 to 200 on the vm hdd and from 50 stable to 10-15 unstable on theiscsi hdd`s. It dosen`t matter how much ram i give the vm. It can be a value from 384 to 2048 and i/o is perfectly, but what is casing this slow i/o on the host when giving the vm more than 2048 mb ram. I don`understand this.

My config is:

2 x Supermicro Server with 16 GB RAM and XÈON Proz. connected via FC to an Supermicro SAN with 16 HDD`S in an RAID 5.

Can anyone help me?

Greetings

Michael

Message was edited by: Ken.Cline to include VMware Server in subject

[weinstein5]

How many other vms do you have running on this host?

[mfgoenk]

there are running 4 other vm`s. all vm`s on this host are using 9 gb ram together and they are allowed to swap some memory. there are also 7 gb left for the host.

greetings

[Ken_Cline]

What VMware product are you using? What is your host OS?

Ken Cline

Technical Director, Virtualization

Wells Landers

VMware Communities User Moderator

[mfgoenk]

VMware 1.04 and Windows2003 R2 SP2 with all Hotfixes 64 Bit