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disk io throughput

Hi friends,

I am new to vmware esx.

I am facing some issue with the disk IO throughput on the rhel5.3 vm's.

My senario is:-

esx server 3.5 is installed on the host's the local disk.

esx server is connected with eqlogic san storage with physical iscsi hba card.

SAN LUN is formate with vmfs where i am creating the virtual machines and the vmdk files.

On virtual machine i installed rhel5.3 and disks are formated with ext3 (4k)

I installed the oracle database on rhel5.3 and the performance is low.

oem is showing the cpu is waiting for to complete the disk io on hight level.

I tested the ext3 filesystem with the iometer utility and the transfer rate i am getting is hardly 10mbps.

please suggest me to resolve this issue.

Thanks & Regards,


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2 Replies

Virtual disks (vmdks) are created in zeroedthick mode by default.

zeroedthick (default) .

Space required for the virtual disk is allocated during creation. Any data remaining on the physical device is not erased during creation, but will be zeroed out at a later time during virtual machine read and write operations.


Space required for the virtual disk is allocated at creation time. Unlike with the zeroedthick format, the data remaining on the physical device is zeroed out during creation. Disks in this format might take much longer to create than other types of disks.


Space required for the virtual disk is allocated during creation. This type

of formatting doesn.t zero out any old data that might be present on this allocated space.

So you just need to create manually vmdk as eagerzeroedthick with vmkfstools or just run IOmeter again.


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EMCCAe, HPE ASE, MCITP: SA+VA, VCP 3/4/5, VMware vExpert XO (14 stars)
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Hi Friends,

Actully the issue was with my iscsi hba card. There was a bottleneck on my hba card (execution throttle).

I changed the value to 128 on the bios level and the issu resolved.

Note:- do proper queuedepth configuration to get the good io performance.

I am closing this thread. I cannot see any closing option here. Please help me.

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