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List: cassandra-user
Subject: Re: Changing num_tokens and migrating to 4.0
From: Alex Ott <alexott () gmail ! com>
Date: 2021-03-20 17:00:52
Message-ID: CALV1_=Lah=wRxEb=4BJYvz8kTMC6D1-aUPFg9ZkA3G6nz95umw () mail ! gmail ! com
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if the nodes are almost the same, except the disk space, then giving them
more may make siltation worse - they will get more requests than other
nodes, and won't have resources to process them.
In Cassandra the disk size isn't the main "success" factor - it's a memory,
CPU, disk type (SSD), etc.
On Sat, Mar 20, 2021 at 5:26 PM Lapo Luchini <lapo@lapo.it> wrote:
> Hi, thanks for suggestions!
> I'll definitely migrate to 4.0 after all this is done, then.
>
> Old prod DC I fear can't suffer losing a node right now (a few nodes
> have the disk 70% full), but I can maybe find a third node for the new
> DC right away.
>
> BTW the new nodes have got 3× the disk space, but are not so much
> different regarding CPU and RAM: does it make any sense giving them a
> bit more num_tokens (maybe 20-30 instead of 16) than the rest of the old
> DC hosts or "asymmetrical" clusters lead to problems?
>
> No real need to do that anyways, moving from 6 nodes to (eventually) 8
> should be enough lessen the load on the disks, and before more space is
> needed I will probably have more nodes.
>
> Lapo
>
> On 2021-03-20 16:23, Alex Ott wrote:
> > I personally maybe would go following way (need to calculate how many
> > joins/decommissions will be at the end):
> >
> > * Decommission one node from prod DC
> > * Form new DC from two new machines and decommissioned one.
> > * Rebuild DC from existing one, make sure that repair finished, etc.
> > * Switch traffic
> > * Remove old DC
> > * Add nodes from old DC one by one into new DC
> >
>
>
>
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>
--
With best wishes, Alex Ott
http://alexott.net/
Twitter: alexott_en (English), alexott (Russian)
[Attachment #3 (text/html)]
<div dir="ltr"><div>if the nodes are almost the same, except the disk space, then \
giving them more may make siltation worse - they will get more requests than other \
nodes, and won't have resources to process them.</div><div>In Cassandra the disk \
size isn't the main "success" factor - it's a memory, CPU, disk \
type (SSD), etc.<br></div></div><br><div class="gmail_quote"><div dir="ltr" \
class="gmail_attr">On Sat, Mar 20, 2021 at 5:26 PM Lapo Luchini <<a \
href="mailto:lapo@lapo.it">lapo@lapo.it</a>> wrote:<br></div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex">Hi, thanks for suggestions!<br> I'll \
definitely migrate to 4.0 after all this is done, then.<br> <br>
Old prod DC I fear can't suffer losing a node right now (a few nodes <br>
have the disk 70% full), but I can maybe find a third node for the new <br>
DC right away.<br>
<br>
BTW the new nodes have got 3× the disk space, but are not so much <br>
different regarding CPU and RAM: does it make any sense giving them a <br>
bit more num_tokens (maybe 20-30 instead of 16) than the rest of the old <br>
DC hosts or "asymmetrical" clusters lead to problems?<br>
<br>
No real need to do that anyways, moving from 6 nodes to (eventually) 8 <br>
should be enough lessen the load on the disks, and before more space is <br>
needed I will probably have more nodes.<br>
<br>
Lapo<br>
<br>
On 2021-03-20 16:23, Alex Ott wrote:<br>
> I personally maybe would go following way (need to calculate how many <br>
> joins/decommissions will be at the end):<br>
> <br>
> * Decommission one node from prod DC<br>
> * Form new DC from two new machines and decommissioned one.<br>
> * Rebuild DC from existing one, make sure that repair finished, etc.<br>
> * Switch traffic<br>
> * Remove old DC<br>
> * Add nodes from old DC one by one into new DC<br>
><br>
<br>
<br>
<br>
---------------------------------------------------------------------<br>
To unsubscribe, e-mail: <a href="mailto:user-unsubscribe@cassandra.apache.org" \
target="_blank">user-unsubscribe@cassandra.apache.org</a><br> For additional \
commands, e-mail: <a href="mailto:user-help@cassandra.apache.org" \
target="_blank">user-help@cassandra.apache.org</a><br> <br>
</blockquote></div><br clear="all"><br>-- <br><div dir="ltr" \
class="gmail_signature"><div dir="ltr"><div>With best wishes, \
Alex Ott<br><a href="http://alexott.net/" \
target="_blank">http://alexott.net/</a><br>Twitter: alexott_en (English), alexott \
(Russian)<br></div></div></div>
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