<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 12, 2016 at 1:43 PM, Gandalf Corvotempesta <span dir="ltr"><<a href="mailto:gandalf.corvotempesta@gmail.com" target="_blank">gandalf.corvotempesta@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="">2016-07-12 9:46 GMT+02:00 Anuradha Talur <<a href="mailto:atalur@redhat.com">atalur@redhat.com</a>>:<br>
> Yes you can add single node with 3 bricks. But, given that you are keeping the replica count<br>
> same, these three bricks will be replica of each other. It is not so useful in case of node<br>
> failures/shutdown.<br>
<br>
</span>So, the only way to grow a replica 3 cluster is to add 3 nodes at once?<br>
This is expensive, about this Ceph is cheaper as I can add a single<br>
OSD node and Ceph automatically rebalance everything and still keep<br>
redundancy<br></blockquote><div><br>Alternatively you can replace 4 selected bricks on the first 3 nodes with the 4
disks on the new machine. Now you have 4 bricks that can be reused.
Form extra 2 replica sets with 3 bricks each and you are done.<br><br></div><div>Example:<br></div><div>You have S1, S2, S3 and you added S4<br></div><div>Lets say the bricks in replica pairs are:<br></div><div>(s1b1, s2b1, s3b1)<br>(s1b2, s2b2, s3b2)<br>(s1b3, s2b3, s3b3)<br>(s1b4, s2b4, s3b4)<br>(s1b5, s2b5, s3b5)<br>(s1b6, s2b6, s3b6)<br></div><div> <br></div><div>Lets say the new bricks are: s4b1, s4b2... s4b6<br><br></div><div>Now you do replace brick of<br>s1b1 -> s4b1<br>s2b2 -> s4b2<br></div><div>s3b3 -> s4b3<br></div><div>s1b4 -> s4b4<br><br></div><div>Now do erase the old bricks that we replaced i.e. s1b1, s2b2, s3b3, s1b4<br><div>add-brick of<br>(s1b1, s2b2, s4b5)<br></div><div>(s1b4, s3b3, s4b6)<br><br></div><div>do rebalance.<br></div><div><br></div><div>I didn't think too much about how to optimize data movement yet. But I am just offering an alternative to the traditional way to add new bricks. I am not sure if this is incorporated in heketi project yet which lets users only care about nodes and not at the bricks level. I guess with heketi, all you need to say is, here take this new machine S4 and it will(should) take care of all this for the users.<br></div><div><br></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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</div></div></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">Pranith<br></div></div>
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