Re: [Xen-users] 4KB Sector Disks

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-06-05 at 07:47 +0100, Gordan Bobic wrote:
> I just thought I'd mention this because it turned out to be the cause of 
> disk I/O performance issues I've been having. For the arhchive/search 
> engines of nothing else.
> 
> Setup:
> 
> Storage server (Linux):
> 1) ZFS zvol backed images, ZFS configured for 4KB sector disks
> 2) IETD iSCSI server
> 
> dom0 (Linux):
> 3) Open-iSCSI client (Linux)
> 
> domU is Windows.

Does Windows know about 4k sectors, or does that end at #3? I can
imagine that doing a read/modify/write for each 512 bytes written would
kill performance.

You mention qemu so I guess this is using emulated IDE -- I'd be very
surprised if that supported anything other than 512b sectors, perhaps
the upstream qemu version might but I doubt the Xen traditional fork
does. I don't know if it is possible to get PV drivers into the Windows
installer super early but if it was (driver disk?) that would be useful,
otherwise installing them ASAP after initial install would seem wise.

The only other thing which springs to mind is enabling jumbo frames on
the network path. Not sure how critical that is these days with GSO and
GRO etc.

Ian.



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