Re: [Xen-users] Xen Sparse Image Files and MaxIQ SSD

[George Shuklin <nge@xxxxxxxx>]

That's simple: caching only if data  exists.

All 'holes' in spare file does not exists. They are just opinion of
filesystem, but on block level there is no sparse.

One more: MaxIQ cache most reed data. Do you often read holes from
sparse?


Ð ÐÑÐ, 08/07/2010 Ð 16:08 -0500, Andy Pace ÐÐÑÐÑ:
> Hello list!
> 
>  
> 
> Iâm currently storing Xen sparse image files for VMâs on remote
> attached storage devices, and looking to increase the amount of IO
> available on it. Iâve ran across MaxIQ SSD read acceleration caching,
> and was wondering if this is a smart move, given the way we use the
> sparse image files.
> 
>  
> 
> My fear is that the MaxIQ will cache entire image files, instead of
>  the most commonly accessed files *INSIDE* the VM. Can anyone confirm
> or deny my theory? 
> 
>  
> 
> Iâve talked with Adaptec and this is what they told me:
> 
>  
> 
> --------
> 
> It's hard to say exactly. Keep in mind that a RAID card isn't aware of
> files, only blocks. So depending on how the blocks are accessed, the
> MaxIQ product may or may not help you. My first impression with 30GB
> files is that it may not be very helpful.
> 
> --------
> 
>  
> 
> So, that being said, right now we are accessing the image files using
> the âfileâ mode:
> 
>  
> 
>     <disk type='file' device='disk'>
> 
>       <driver name='file'/>
> 
>       <source file='/distributed/vms/29609/disk.img'/>
> 
>       <target dev='xvda' bus='xen'/>
> 
>     </disk>
> 
>  
> 
> Will the MaxIQ work in the way I want it to, or will I have to change
> the way we access the images? Or will it end up trying to cache entire
> images onto the SSD? Has anyone had experience with this type of
> application?
> 
> 
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