8-STABLE Slow Write Speeds on ESXI 4.0

[Joshua Boyd]

On Mon, Aug 9, 2010 at 12:38 PM, Ivan Voras <ivoras at freebsd.org> wrote:

> On 9 August 2010 18:11, Jeremy Chadwick <freebsd at jdc.parodius.com> wrote:
>
> > I thought Intel VT-d was supposed to help address things like this?
>
> Probably -
> http://www.intel.com/technology/itj/2006/v10i3/2-io/7-conclusion.htm
> says it should help unmodified guests, but I don't know for sure. I do
> know that Nehalems run faster on VMWare, probably because "nested
> paging" or whatever it's called helps context switches on syscalls.
>
> > I can confirm on VMware Workstation 7.1, not ESXi, that disk I/O
> > performance isn't that great.  I only test with a Host OS of Windows XP
> > SP3, and for the Guest OS's hard disk driver use the LSI SATA/SAS
> > option.  I can't imagine IDE/ATA being faster, since (at least
> > Workstation) emulates an Intel ICH2.
>
> Yes, disk IO was always slow with VMWare. VirtualBox cheats by
> emulating ATA controllers (ICH6) instead of SCSI and turning on disk
> cache - it's noticably faster than VMWare.
>

I've only tried the SAS/SCSI controllers in ESXI. Perhaps I should try
ATA...


>
> > I was under the impression that ESXi provided native access to the
> > hardware in the system (vs. Workstation which emulates everything)?
>
> I think it can be configured this way, but then you'd need a separate
> LUN for the VM drive, bypassing vmware's usual storage (vmfs) and all
> the goodies that come with it. OTOH, there are paravirtualized drivers
> for Linux and Windows in 4.0 which should help, but I haven't tried
> them yet.
>

It can be configured this way, but then you'd have to pre-allocate LUNs for
each of your VMs ... not all that convenient.


>
> > The controller seen by FreeBSD in the OP's system is:
> >
> > mpt0: <LSILogic SAS/SATA Adapter> port 0x4000-0x40ff mem
> 0xd9c04000-0xd9c07fff,0xd9c10000-0xd9c1ffff irq 18 at device 0.0 on pci3
> > mpt0: [ITHREAD]
> > mpt0: MPI Version=1.5.0.0
> >
> > Which looks an awful lot like what I see on Workstation 7.1.
> >
> > FWIW, Workstation 7.1 is fairly adamant about stating "if you want
> > faster disk I/O, pre-allocate the disk space rather than let disk use
> > grow dynamically".  I've never tested this however.
>
> Yes, this statement has always been true.
>
> > How does Linux's I/O perform with the same setup?
>
> I've tested Linux, Windows and FreeBSD on VMWare 3.5 last year and the
> results (IOPS) were:
>
> ESXi-FreeBSD    174
> ESXi-Linux      221
> ESXI-Windows    98
> Xen-FreeBSD     72
> Xen-Linux       148
> Xen-Linux-PV    244
> HyperV-FreeBSD  61
> HyperV-Linux    69
> HyperV-Windows  58
>
> (I couldn't get Windows to run on Xen; "Linux-PV" is Linux as
> paravirtualized Xen guest).
>



-- 
Joshua Boyd
JBipNet

E-mail: boydjd at jbip.net

http://www.jbip.net