<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Oct 30, 2016 at 12:47 PM, Mike (maillinglists) <span dir="ltr"><<a href="mailto:maillist@probie.nl" target="_blank">maillist@probie.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Yaniv,<br>
<br>
Op 30-10-2016 om 11:35 schreef Yaniv Kaul:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
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On Sun, Oct 30, 2016 at 12:02 PM, Mike (maillinglists)<br></span><span class="">
<<a href="mailto:maillist@probie.nl" target="_blank">maillist@probie.nl</a> <mailto:<a href="mailto:maillist@probie.nl" target="_blank">maillist@probie.nl</a>>> wrote:<br>
<br>
Hi guys,<br>
<br>
There have been a few related questions already that I could find,<br>
but I did not find anything relating to my specific use case.<br>
<br>
Currently it is not possible to mix local storage with shared<br>
storage in the same datacenter.<br>
The reason seems to be because of the storage pool manager (SPM).<br>
This is a role in the datacenter provided to one specific host.<br>
<br>
While I understand that this makes having local storage impossible,<br>
I believe there is a use case to have local storage in a shared<br>
storage datacenter.<br>
<br>
<br>
Indeed, this is one of the more appealing use cases. There are others s<br>
well.<br>
<br>
<br>
Consider the following:<br>
I have a few applications that require 1 milli second latency and at<br>
most 2 milli second.<br>
<br>
<br>
For read, write or both?<br>
</span></blockquote>
Both I'm afraid.<span class=""><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br>
That is not consistenly achievable with shared storage, to that end<br>
I added flash storage to a few hypervisors.<br>
<br>
<br>
You could have flash on your shared storage.<br>
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The problem with shared flash storage is the storage network required in between. I have seen shared NFS storage at 1ms latency, but that has not been stable and this application requires stable 1ms latencies.<span class=""><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br>
About 5% of my servers require this and are not that resource hungry<br>
to require a dedicated physical server.<br>
That same 5% also has no requirement to be migrated if a host fails.<br>
<br>
So in short I have 5 heavy hosts running ovirt with a shared storage<br>
domain on NFS for 95% of my servers.<br>
All running fine, but I am now unable to run my remaining 5%.<br>
<br>
<br>
Perhaps, if there are no HA requirements, those VMs with local domain<br>
needs can be in their own DC, a local one? If it's just 5%, shouldn't be<br>
much of an effort?<br>
</blockquote></span>
Can a host be in 2 datacenters?<br></blockquote><div><br></div><div>No, I suggested to dedicate a host (or several) with their own local DC for those 5%.</div><div>Y.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
I was not aware of this and I will investigate.<span class=""><br>
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<br>
<br>
To finish up my summary I have been testing various virtualization<br>
technologies, like VmWare and Hyper-V.<br>
They allow such configurations as I mentioned.<br>
<br>
I already had some chat on irc with various guys and they suggested<br>
that I put this on the mailing list, so here goes.<br>
<br>
My suggestion would be to evoluate from SPM to SDM.<br>
<br>
<br>
Easier said than done... We have worked on this for quite some time,<br>
it's not as easy as one might think.<br>
</blockquote></span>
I appreciate your honousty, but still hope this can be achieved.<span class=""><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br>
SDM stands for Storage Domain Manager.<br>
This would create the possibility to have all nodes in the<br>
datacenter participate in the storage handling.<br>
A extra benefit would be that local storage could be added.<br>
<br>
What do you think?<br>
<br>
<br>
There are other use cases we think flash on the host can be used, some<br>
may be of use for your use case.<br>
For example, dm-cache[1].<br>
<br>
We are still looking at this. I think Gluster already can make use it<br>
for cache, for example.<br>
Y.<br>
</blockquote></span>
Gluster is an angle we are investigating, but takes time to look into. Thanks!<br>
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[1] <a href="https://people.redhat.com/mskinner/rhug/q1.2016/dm-cache.pdf" rel="noreferrer" target="_blank">https://people.redhat.com/mski<wbr>nner/rhug/q1.2016/dm-cache.pdf</a><br>
</blockquote>
Thanks!<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
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<br>
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Thanks for reading.<br>
<br>
Kind regards,<br>
Mike van Goor<br>
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