Re: [Xen-users] Physical Disk VBD vs File VBD Performance

["Michael T. Babcock" <mike@xxxxxxxxxxxxxx>]

Matias wrote:
> Correct me if I'm wrong, when writing
> to RAID5 the data gets striped up and your write performance increases.
> Now if I write to the dom2 it has to write the whole data to one spindle.
RAID5 frequently causes performance losses, not gains, although with 
high performance controllers and disks you can see performance 
improvements over a raw disk.  The problem is that the data isn't just 
striped like in a RAID-0 set, the data has to have parity information 
calculated and written out as well, and all disks get hit with write 
requests at the same time when writing out data.  On reads (in a 
non-degraded set), you may see performance increases because of the 
striped nature of the data, but no guarantees.
--
Michael T. Babcock
http://mikebabcock.ca


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