<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">The host is some linux or other? Running with that assumption, I don't expect you will get anything extra out of zfs if you are only using it for pooling vs. LVM. As long as you are handing a block device to the guest, the IO overhead of the virtualization is pretty much nil. Now, if you were using regular files to back your virtual drives instead of block devices, ZFS (not just zpool) on the host might get you something, but I depends on a lot of things, and I would never advocate putting a file system on a file system if you care at all about IO. That's where your IO overhead comes in. Passing it to a KVM/libvirt guest does not introduce anything of concern on modern hardware (maybe an extra processor instruction or 2 here and there).</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">If you don't already know and love ZFS with all its beauty and risks, and you don't have a specific critical need for it, I recommend against it. ext4 on LVM does a great job for 99.99% of use cases and the support and user community for it is second to none. I found this not to be the case with FreeNAS/BSD/ZFS when I had a year long nightmare with it some time ago on what is admittedly now likely and aged version of ZFS.</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Aug 21, 2015 at 3:33 PM, Bruce Dawson <span dir="ltr"><<a href="mailto:jbd@codemeta.com" target="_blank">jbd@codemeta.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
For this rainy weekend, please consider the following:<br>
<br>
I'm constructing a new server and want 2 KVM guest systems on it.
There are 3 4TB drives on it. At the moment, assume one 4TB drive
will be reserved for the KVM host. The server has 16GB of RAM.<br>
<br>
What are the advantages/disadvantages of:<br>
<ol>
<li>Putting all disks in a ZFS pool on the host and dividing the
pool between each guest. Or:</li>
<li>Giving each guest its own disk. (At least one of the guests
will be running ZFS).</li>
</ol>
<p>The guests will be:<br>
</p>
<p> * Both guests will be running DNS servers<br>
* One guest will be running a Postfix/Dovecot mail server
(including mailman)<br>
* The other guest will be running a LAMP stack.<br>
</p>
<p>Hints: <br>
* I don't particularly like option 2 as I'll lose the benefits
of ZFS (snapshot backups, striping, ...)<br>
* I don't know if the performance benefits of ZFS will outweigh
the overhead of KVM/libvirt.<span class="HOEnZb"><font color="#888888"><br>
</font></span></p><span class="HOEnZb"><font color="#888888">
<p>--Bruce<br>
</p>
</font></span></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><span style="font-family:verdana,sans-serif">Alan Johnson</span><br></div><div><font face="verdana, sans-serif"><a href="mailto:alan@datdec.com" target="_blank">alan@datdec.com</a></font><div><span style="font-size:16px;font-variant:small-caps;text-align:center;background-color:rgb(255,255,255)"><a href="http://xkcd.com/1179/" target="_blank"><font face="verdana, sans-serif">Date Format PSA</font></a></span></div></div></div></div></div></div>
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