Re: [Xen-API] XCP 1.6 and 4k alignment

[George Shuklin <george.shuklin@xxxxxxxxx>]

I done some digging in VHD format, so here some information:

Every VHD consists from chunks 2M+4k size (2*1024*1024 + 4*1024 bytes). 
Payload is aligned, bitmap (512 bytes not aligned, but padding bytes at 
the begin of the chunk solve the problem). IO on underlaying storage is 
aligned, but can be very slow because 1st write in VHD file cause 
massive 2Mb writeback due Copy-on-Write operations.
There is some strange issues I saw during tests when write operations 
cause significant read operations from VHD layer, but on normal storage 
this is not a grave problem (but still a somehow performance loss).
06.05.2013 15:58, dominic.ryan@xxxxxxxxx ÐÐÑÐÑ:
> Hi All,
>
> Just wondering if there is a documented method to create a Storage 
> Repository on a local SSD so that it is 4k aligned? I've also 
> installed XCP itself on this SSD, but elected not to create a storage 
> respository during installtion in the hope there is a manual method 
> that facilitates 4k alignment. Thanks.
>
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