Couple of quetsions HD perf, mac address...

DISCUSSION Benjamin Budts 3 participants 4 messages Jul 3, 2007 3 messages not in the archive KVM

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Benjamin Budts

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2007-07-03 09:43 UTC #0 lore raw

Hi there,

Sorry to bother the developpers list, I have couple of questions...

I've been testing kvm for couple of months with the following hardware :
S5000pal intel board
1x Duo Core Xeon 2.4
2048Gb DDR2 667 Ram
Western digital SATA 150 10K rpm disk.

I run kvm21 at the moment...(I need to upgrade asap of course ;) )

And have the following questions :

1* When i run hdparm -t /dev/sda1 I have 80-85Mbit/s read speed on my guest os (debian etch)

If I run it ''in'' a virtual machine (using also debian Etch with 2.6.21.5 kernel) I get : 28-35Mbits...

I even tried to put the image on a seperate disk to be able to have more, but I can't get more then 35Mbits out of it...

How can I up the disk performance without having to replace everything by SCSI hardware ?

2* When will smp be supported in the VM ? Would love to test the performance by starting up the virtual machine with the -smp 2 command...Kernel hangs at the moment
(I read you guys put it on the commit list, and you're working on it...)

3* When I specify a mac address for my debian virtual machine eth0 changes to eth3 ... very very weird... it's not that bad, i just changed my interfaces config file from eth0 to eth3, but it's a bit weird

My windows xp seems to boot without a problem when specifying another mac addr

Did you guys have that problem yet ? How can I fix it please ?

Keep up the good work, lovely product !

thx
Ben

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Dor Laor

2007-07-03 11:48 UTC #2 lore raw

Quoted 11 lines

1* When i run hdparm -t /dev/sda1 I have 80-85Mbit/s read speed on my guest os (debian etch)
If I run it ''in'' a virtual machine (using also debian Etch with 2.6.21.5 kernel) I get : 28-35Mbits...
I even tried to put the image on a seperate disk to be able to have more, but I can't get more then 35Mbits out of it...
How can I up the disk performance without having to replace everything by SCSI hardware ?

As Greg mentioned, PV-scsi drivers are good when implemented. There is also unmerged PV driver for ide disks developed by RedHat. By the end of the year we'll probably handle it better.

Quoted 5 lines

2* When will smp be supported in the VM ? Would love to test the performance by starting up the virtual machine with the -smp 2 command...Kernel hangs at the moment
(I read you guys put it on the commit list, and you're working on

it...)

It's work in progress, the current state is that smp Linux can boot but it's
not stable yet. I guess it's a matter of several months to stabilze.

Laurent Vivier

2007-07-03 11:51 UTC #3 lore raw

In reply to a message not in the archive

Benjamin Budts wrote:
[snip]

Quoted 12 lines

1* When i run hdparm -t /dev/sda1 I have 80-85Mbit/s read speed on my guest os (debian etch)
If I run it ''in'' a virtual machine (using also debian Etch with 2.6.21.5 kernel) I get : 28-35Mbits...
I even tried to put the image on a seperate disk to be able to have more, but I can't get more then 35Mbits out of it...
How can I up the disk performance without having to replace everything by SCSI hardware ?

You can improve performance by using virtual SCSI disks. I post some benchchmarks with dbench on this list at the end of may (24/05).

QEmu (and thus KVM) doesn't support natively SCSI disk for the PC virtual machine. I post a patch the 1st of march on QEmu mailing list to add a "-sda" parameter to use SCSI disk (but my approach was not approved by maintainers). The problem with the virtual SCSI is you cannot boot on it because there is no BIOS to manage it. But you can use it as storage and boot linux using the parameter "-kernel" to load directly the kernel from the host disk.

Regards,
Laurent

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------------- Laurent.Vivier-6ktuUTfB/[email protected]  --------------
       "Any sufficiently advanced technology is
  indistinguishable from magic." - Arthur C. Clarke

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Laurent Vivier

2007-07-03 15:19 UTC #6 lore raw

Quoted 5 lines · Benjamin Budts

Hi Laurent,
Intresting stuff, could you send me your patch and the benchmarks please ? I think I might try it out.

patch:

http://permalink.gmane.org/gmane.comp.emulators.qemu/15969

benchmarks:

http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/3373

Quoted 38 lines

thx a lot
Quoted 33 lines · Laurent Vivier
Benjamin Budts wrote:
[snip]
Quoted 13 lines
1* When i run hdparm -t /dev/sda1 I have 80-85Mbit/s read speed on my guest os (debian etch)
If I run it ''in'' a virtual machine (using also debian Etch with 2.6.21.5 kernel) I get : 28-35Mbits...
I even tried to put the image on a seperate disk to be able to have more, but I can't get more then 35Mbits out of it...
How can I up the disk performance without having to replace everything by SCSI hardware ?
You can improve performance by using virtual SCSI disks. I post some benchchmarks with dbench on this list at the end of may (24/05).
QEmu (and thus KVM) doesn't support natively SCSI disk for the PC virtual machine. I post a patch the 1st of march on QEmu mailing list to add a "-sda"
parameter to use SCSI disk (but my approach was not approved by maintainers).
The problem with the virtual SCSI is you cannot boot on it because there is no
BIOS to manage it. But you can use it as storage and boot linux using the parameter "-kernel" to load directly the kernel from the host disk.
Regards,
Laurent

Signature · 3 lines

------------- Laurent.Vivier-6ktuUTfB/[email protected]  --------------
       "Any sufficiently advanced technology is
  indistinguishable from magic." - Arthur C. Clarke

_______________________________________________
kvm-devel mailing list [email protected]
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