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

[Andy Pace <APace@xxxxxxxxxxxxx>]

Right, but the data does exist. What I'm wondering is if it will treat the 
sparse image file as 1 file, or will it cache on a block basis.

> Do you often read holes from sparse?

I'm not sure how to answer that.

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of George Shuklin
Sent: Thursday, July 08, 2010 4:36 PM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen Sparse Image Files and MaxIQ SSD

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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