<div dir="ltr"><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">Hi All,</div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif"><br></div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">
Thanks for clarifying the Cinder behavior w.r.t a snapshot & its clones which seems to be independent/decoupled.</div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">The current volume & its snapshot based validations in Cinder holds true for snapshot & its clones w.r.t my storage requirements. </div>
<div class="gmail_default" style="font-family:'trebuchet ms',sans-serif"><br></div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">Our storage is built on top of ZFS filesystem. </div>
<div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">The volume -> snapshot -> clone that I am referring to in turn points to a ZFS dataset -> ZFS snapshot -> ZFS clone.</div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">
<br></div><div class="gmail_default" style="font-family:'trebuchet ms',sans-serif">The best part of ZFS based snapshots & clones are :</div><div class="gmail_default"><ul><li><font face="trebuchet ms, sans-serif">these are almost instantaneous ( i.e. copy-on-write based copies)</font></li>
<li><font face="trebuchet ms, sans-serif">these will not consume any additional (initially)</font></li><ul><li><font face="trebuchet ms, sans-serif"><span style="color:rgb(0,0,0)">a clone initially shares all its disk space with the original snapshot, its </span><span class="" style="color:rgb(0,0,0)">used</span><span style="color:rgb(0,0,0)"> property is initially zero. </span></font></li>
<li><font face="trebuchet ms, sans-serif"><span style="color:rgb(0,0,0)">As changes are made to the clone, it uses more space. </span></font></li><li><font face="trebuchet ms, sans-serif"><span style="color:rgb(0,0,0)">The </span><span class="" style="color:rgb(0,0,0)">used</span><span style="color:rgb(0,0,0)"> property of the original snapshot does not consider the disk space consumed by the clone.</span><br>
</font></li></ul></ul><div><font color="#000000" face="trebuchet ms, sans-serif">Further optimizations i.e. cool feature:</font></div><div><ul><li><font color="#000000" face="trebuchet ms, sans-serif">While creating VM clones, a hypervisor driver can delegate part of its cloning process to storage driver & hence, the overall VM cloning will be very very fast.</font></li>
</ul></div><div><br></div><div><font color="#000000" face="Times New Roman" size="3"><br></font></div></div></div><div class="gmail_extra"><br clear="all"><div><div dir="ltr"><div><font style="background-color:rgb(255,255,255)" color="#000000" face="trebuchet ms, sans-serif">Regards,</font></div>
<font style="background-color:rgb(255,255,255)" color="#000000" face="trebuchet ms, sans-serif">Amit</font><div><a href="http://www.cloudbyte.com/" target="_blank"><font style="background-color:rgb(255,255,255)" color="#0000ff" face="trebuchet ms, sans-serif"><i>CloudByte Inc.</i></font></a></div>
</div></div>
<br><br><div class="gmail_quote">On Thu, Jun 19, 2014 at 9:16 PM, John Griffith <span dir="ltr"><<a href="mailto:john.griffith@solidfire.com" target="_blank">john.griffith@solidfire.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div class="gmail_default" style="font-family:courier new,monospace"><br></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div class="">On Tue, Jun 17, 2014 at 10:50 PM, Amit Das <span dir="ltr"><<a href="mailto:amit.das@cloudbyte.com" target="_blank">amit.das@cloudbyte.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div style="font-family:trebuchet ms,sans-serif">Hi Stackers,</div><div style="font-family:trebuchet ms,sans-serif">
<br></div><div style="font-family:trebuchet ms,sans-serif">
I have been implementing a Cinder driver for our storage solution & facing issues with below scenario.</div><div style="font-family:trebuchet ms,sans-serif"><br></div><div style="font-family:trebuchet ms,sans-serif">
Scenario - When a user/admin tries to delete a snapshot that has associated clone(s), an error message/log should be shown to the user stating that '<i>There are clones associated to this snapshot. Hence, snapshot cannot be deleted</i>'. </div>
</div></blockquote><div> </div></div><div class="gmail_default" style="font-family:'courier new',monospace">What's the use model of "clones associated with the snapshot"? What are these "clones" from a Cinder perspective. Easy answer is: don't create them, but I realize you probably have a cool feature or optimization that you're trying to leverage here.</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">
<div style="font-family:trebuchet ms,sans-serif"><br></div><div style="font-family:trebuchet ms,sans-serif">Implementation issues - If Cinder driver throws an Exception the snapshot will have error_deleting status & will not be usable. If Cinder driver logs the error silently then Openstack will probably mark the snapshot as deleted.</div>
</div></blockquote><div><br></div><div class="gmail_default" style="font-family:'courier new',monospace">So as others point out, from a Cinder perspective this is what I/we would expect. </div><div class="gmail_default" style="font-family:'courier new',monospace">
<br></div><div class="gmail_default" style="font-family:'courier new',monospace">Scott made some really good points, but the point is we do not want to behave differently for every single driver. The agreed upon mission for Cinder is to actually provide a consistent API and set of behaviors to end users regardless of what backend device they're using (in other words that should remain pretty much invisible to the end-user).</div>
<div class="gmail_default" style="font-family:'courier new',monospace"><br></div><div class="gmail_default" style="font-family:'courier new',monospace">What do you use the Clones of the Snapshot for? Maybe we can come up with another approach that works and keeps consistency in the API.</div>
<div class="gmail_default" style="font-family:'courier new',monospace"><br></div><div class="gmail_default" style="font-family:'courier new',monospace"><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div style="font-family:trebuchet ms,sans-serif"><br></div><div style="font-family:trebuchet ms,sans-serif">What is the appropriate procedure that needs to be followed for above usecase.</div>
<div style="font-family:trebuchet ms,sans-serif"><br></div><div><div dir="ltr"><div><font style="background-color:rgb(255,255,255)" color="#000000" face="trebuchet ms, sans-serif">Regards,</font></div>
<font style="background-color:rgb(255,255,255)" color="#000000" face="trebuchet ms, sans-serif">Amit</font><div><a href="http://www.cloudbyte.com/" target="_blank"><font style="background-color:rgb(255,255,255)" color="#0000ff" face="trebuchet ms, sans-serif"><i>CloudByte Inc.</i></font></a></div>
</div></div>
</div>
<br>_______________________________________________<br>
OpenStack-dev mailing list<br>
<a href="mailto:OpenStack-dev@lists.openstack.org" target="_blank">OpenStack-dev@lists.openstack.org</a><br>
<a href="http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev" target="_blank">http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev</a><br>
<br></blockquote></div><br></div></div>
<br>_______________________________________________<br>
OpenStack-dev mailing list<br>
<a href="mailto:OpenStack-dev@lists.openstack.org">OpenStack-dev@lists.openstack.org</a><br>
<a href="http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev" target="_blank">http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev</a><br>
<br></blockquote></div><br></div>