Server2008 R2 - slow hdd speed test on C drive(OS) Virtual machine

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I've got a small issue I'd like advice on:

Server 2008 R2 64bit  Virtual machine, running on ESXi 5.5

3 vdisks make up the VM.
c drive - 150GB
d drive - 150GB
e drive - 150 GB

Storage is HP MSA P2000 G3
Qlogic SANBOX 5800

Virtual machine vdisks located on 600GB SAS drives 15K making up a 1.8TB volume.

My issue is that in the c drive I get 200Mbps speeds
On the d and e drive I get 1.5Gbps speeds

Why slower on the c drive, all drives using same Volume 15K SAS drives.
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can you check how it is connected to esxi i.e. the interface, SCSI, SAS etc.
Distinguished Expert 2018

How much free space left in C drive ?

Also what is the page file set in C drive and what is the allocated memory to VM ?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

How are you testing, with a software application?

Is this causing performance issues, or an observation?

How many disks in the SAN?

What RAID type in the SAN?

Are the vdisks owned by the same controller?

Is this FC, SAS or iSCSI?
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Purely observation as VM isn't in production yet.
5 x 600GB SAS 15K drives make up 1.8TB vdisk.

My question is, why only the C drive slow? other drives are on the same SAN vdisk, same volume.


Further investigating suggests must be limitation on drive OS is installed on.
I installed OS on drive1 this time and now drive0 gets high/good speed test results, drive1 slow speed test.

Any comments?
Manjunath SulladTechnical Consultant

Run chkdsk for C drive,

Open computer --> Rt clk on C drive --> Properties --> Tools tab --> Click on Check now.

Wait until it complete the error checks.

Also run sfc /scannow command in elevated command prompt and check the errors.
Server2008 R2 limitation on C drive.


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