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

[dominic.ryan@xxxxxxxxx]

On 2013-05-07 00:31, Adi Kriegisch wrote:
> Hey,
>
> > You mean in the context of using a file to contain the virtual disk
> > image? Just put it on a FS that is using 4KB sectors, and that is
> > aligned to a 4KB boundary, and when you are installing the guest
> > make sure you set up the FS to also use 4KB blocks.
> Hmmm, that depends on what you do within the image: In case you 
> create
> partitions within those images you need to assure that those 
> partitions are
> aligned to use 4K blocks which boils down to using GPT for the 
> partition
> table.
> When you create a file system on the raw image you don't need to do
> anything: the blocks are already aligned and it does not matter what
> blocksize you use for creating the filesystem; so 512B is ok too.
> I actually never used image files but only storage devices like lvm
> volumes. But that depends on the use case, of course.
>
> -- Adi
>
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Thanks for the replies everyone.

Adi, just so I'm 100% clear on this. Are you saying that 4k aligned or 
not is irrelevant due to the 512 hard-coded issue with DomU? Is the 
performance hit you were seeing in your bug report still applicable to 
non RAID environments? Reason I ask is that with a single Windows 2008 
R2 VM on XCP 1.6 all loaded on a Samsung 840 500GB SSD I am getting IOPS 
and transfer rates in IOMeter that are a fraction (as in 5%) of the 
manufacturers claims. I think I'll blow away my XCP install and put 
Windows 2008 R2 on directly and see what I get out of IOMeter there 
using the same testing profiles.
Thanks


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