Re: [Xen-users] SSD 4K Alignment?

[Adi Kriegisch <adi@xxxxxxxxxxxx>]

Hi,

> Just wondering if Xen/XCP aligns local storage to 4K boundaries when
> using 4K formatted storage such as SSD's? If not, is there a
> documented way to manually perform this alignment?
Linux basically does that kind of alignment for you (based on the
information the hardware hands over to the kernel; WD Green disks for
example pretend to have 512B size so the alignment does not work).
But this information is only available on Dom0; the xen storage backend
uses a hardcoded 512B block size for passing devices through to DomU[1].

This has close to no effect when doing all the partitioning and filesystem
creation in Dom0 (where the necessary information is available) or when
manually specifying the correct options to fdisk/mkfs in DomU (which is a
pain). For accessing data, Linux uses a default block size of 4K anyways.

-- Adi

[1] http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1745

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