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Optimizing hard drive performance on Linux Virtual PCs

Source: microsoft.public.virtualpc
Sent: 08/26/2004
From: havuk
Message:

hdparm is a Linux shell utility for viewing and manipulating various IDE
drive and driver parameters. Investigation and testing of multiple Linux
distributions has proved the following configuration to be optimal for most
Virtual PCs:

hdparm -m128 -u1 -c3 -W1 -A1 -d1 -X66 /dev/hda

To test this configuration on a specific Virtual PC, the above command can
be entered in a Linux console. This command does not make any permanent
changes, and the hard drive settings will revert once the Virtual PC is reset.

Once the above command has been tested, the configuration can be made
permanent by adding the command to the top of the /etc/rc.d/rc.local startup
script. To stop hdparm from displaying any output during the boot process,
use the following command:

hdparm -qm128 -qu1 -qc3 -qW1 -qA1 -qd1 -qX66 /dev/hda

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Related Messages

Analysis of the HDPARM parameters

Sent: 08/26/2004
From: havuk
Message:

The recommended hdparm command utilizes a number of configuration parameters.
Below is a list of the parameters used, along with an explanation of what
each parameter does.

-m128 - Enables multiple sector mode (aka IDE Block Mode) and sets the block
size to 128 sectors.
-u1 - Permits Linux to unmask other interrupts while processing a drive
interrupt.
-c3 - Enables 32 bit I/O support with synchronization.
-W1 - Enables the IDE drive's write caching feature.
-A1 - Enables the IDE drive's read-lookahead feature.
-d1 - Enables DMA support on the virtual hard drive.
-X66 - Sets the IDE drive to use Ultra DMA mode2
/dev/hda - Specifies which IDE device to apply the configuration changes to.

Technical analysis of PIO vs. DMA in an emulated environment

Sent: 08/26/2004
From: havuk
Message:

Many Linux distributions use programmed I/O (PIO) over direct memory access
(DMA) for their default method of accessing the hard drive - as some Linux
developers debate the advantages of PIO vs. DMA when running on physical
hardware.

However, in an emulated environment DMA has major advantages over PIO. PIO
sends all hard drive requests through the CPU, so that during a typical hard
drive operation both the CPU and the hard drive controller are heavily
utilized. DMA, on the other hand, communicates directly to the hard drive
controller and side steps the CPU for hard drive activity.

Virtual PC is optimized for DMA to virtualized IDE devices (CD/DVDs and hard
drives). PIO requires one I/O operation (IN/OUT instruction) for every two or
four bytes read from or written to an IDE device. These I/O accesses are
difficult to virtualize, and the overhead for each I/O
access is relatively high. DMA, on the other hand, only requires one I/O
operation for each multisector read or write operation.

Re: Optimizing hard drive performance on Linux Virtual PCs

Sent: 08/26/2004
From: "Benjamin Armstrong [MSFT]" <(email address - cut out)>
Message:

FWIW - this is a direct copy from the old TechRef for VPC 5.2 - available on
Steve's site:

http://www.essjae.com/VPC/virtual_pc_downloads.htm

--
Cheers,
Benjamin Armstrong
======================
Virtual PC Program Manager

This posting is provided "AS IS" with no warranties, and confers no rights.
You assume all risk for your use.

"havuk" <(email address - cut out)> wrote in message
news:(email address - cut out)...

Show quoted text

> hdparm is a Linux shell utility for viewing and manipulating various IDE
> drive and driver parameters. Investigation and testing of multiple Linux
> distributions has proved the following configuration to be optimal for
> most
> Virtual PCs:
>
> hdparm -m128 -u1 -c3 -W1 -A1 -d1 -X66 /dev/hda
>
> To test this configuration on a specific Virtual PC, the above command can
> be entered in a Linux console. This command does not make any permanent
> changes, and the hard drive settings will revert once the Virtual PC is
> reset.
>
> Once the above command has been tested, the configuration can be made
> permanent by adding the command to the top of the /etc/rc.d/rc.local
> startup
> script. To stop hdparm from displaying any output during the boot process,
> use the following command:
>
> hdparm -qm128 -qu1 -qc3 -qW1 -qA1 -qd1 -qX66 /dev/hda
>
>

Re: Optimizing hard drive performance on Linux Virtual PCs

Sent: 08/26/2004
From: Steve Jain <(email address - cut out)>
Message:

But, I cannot take credit for writing it originally, methinks it was
Mr. Ben A.

On Tue, 24 Aug 2004 11:50:30 -0700, "Benjamin Armstrong [MSFT]"
<(email address - cut out)> wrote:

Steve Jain, Microsoft MVP for Virtual PC for Windows
Website: http://www.essjae.com
*** All posts are provided AS-IS, no warranty, no QoS ***

Show quoted text

>FWIW - this is a direct copy from the old TechRef for VPC 5.2 - available on
>Steve's site:
>
>http://www.essjae.com/VPC/virtual_pc_downloads.htm

Re: Optimizing hard drive performance on Linux Virtual PCs

Sent: 08/26/2004
From: "Benjamin Armstrong [MSFT]" <(email address - cut out)>
Message:

Yeah - but I can't find any copies of the original doc online anymore :-)

--
Cheers,
Benjamin Armstrong
======================
Virtual PC Program Manager

This posting is provided "AS IS" with no warranties, and confers no rights.
You assume all risk for your use.

"Steve Jain" <(email address - cut out)> wrote in message
news:(email address - cut out)...

Show quoted text

> But, I cannot take credit for writing it originally, methinks it was
> Mr. Ben A.
>
> On Tue, 24 Aug 2004 11:50:30 -0700, "Benjamin Armstrong [MSFT]"
> <(email address - cut out)> wrote:
>
>>FWIW - this is a direct copy from the old TechRef for VPC 5.2 - available
>>on
>>Steve's site:
>>
>>http://www.essjae.com/VPC/virtual_pc_downloads.htm
>
> Steve Jain, Microsoft MVP for Virtual PC for Windows
> Website: http://www.essjae.com
> *** All posts are provided AS-IS, no warranty, no QoS ***

Re: Optimizing hard drive performance on Linux Virtual PCs

Sent: 08/26/2004
From: Paul Adare - MVP - Microsoft Virtual PC <(email address - cut out)>
Message:

In article <(email address - cut out)>, in the
microsoft.public.virtualpc news group, Benjamin Armstrong [MSFT]
<(email address - cut out)> says...

I knew I'd seen all of that before, just hadn't gotten the cobwebs out
to figure out where. :-)

--
Paul Adare
This posting is provided "AS IS" with no warranties, and confers no
rights.

Show quoted text

> FWIW - this is a direct copy from the old TechRef for VPC 5.2 - available on
> Steve's site:
>

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