Ephemeral is fine, you just need to have enough replicas (in enough AZs and 
enough regions) to tolerate instances being terminated.




From: Vladimir Yudovin <vla...@winguzone.com>
Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
Date: Monday, October 17, 2016 at 11:48 AM
To: user <user@cassandra.apache.org>
Subject: Re: Adding disk capacity to a running node


It's extremely unreliable to use ephemeral (local) disks. Even if you don't 
stop instance by yourself, it can be restarted on different server in case of 
some hardware failure or AWS initiated update. So all node data will be lost.


Best regards, Vladimir Yudovin, 

Winguzone - Hosted Cloud Cassandra on Azure and SoftLayer.
Launch your cluster in minutes.



---- On Mon, 17 Oct 2016 14:45:00 -0400Seth Edwards <s...@pubnub.com> wrote ----


These are i2.2xlarge instances so the disks currently configured as ephemeral 
dedicated disks. 


On Mon, Oct 17, 2016 at 11:34 AM, Laing, Michael <michael.la...@nytimes.com> 


You could just expand the size of your ebs volume and extend the file system. 
No data is lost - assuming you are running Linux.



On Monday, October 17, 2016, Seth Edwards <s...@pubnub.com> wrote:

We're running 2.0.16. We're migrating to a new data model but we've had an 
unexpected increase in write traffic that has caused us some capacity issues 
when we encounter compactions. Our old data model is on STCS. We'd like to add 
another ebs volume (we're on aws) to our JBOD config and hopefully avoid any 
situation where we run out of disk space during a large compaction. It appears 
that the behavior we are hoping to get is actually undesirable and removed in 
3.2. It still might be an option for us until we can finish the migration. 


I'm not familiar with LVM so it may be a bit risky to try at this point. 


On Mon, Oct 17, 2016 at 9:42 AM, Yabin Meng <yabinm...@gmail.com> wrote:

I assume you're talking about Cassandra JBOD (just a bunch of disk) setup 
because you do mention it as adding it to the list of data directories. If this 
is the case, you may run into issues, depending on your C* version. Check this 
out: http://www.datastax.com/dev/blog/improving-jbod.


Or another approach is to use LVM to manage multiple devices into a single 
mount point. If you do so, from what Cassandra can see is just simply increased 
disk storage space and there should should have no problem.


Hope this helps,




On Mon, Oct 17, 2016 at 11:54 AM, Vladimir Yudovin <vla...@winguzone.com> wrote:


Yes, Cassandra should keep percent of disk usage equal for all disk. Compaction 
process and SSTable flushes will use new disk to distribute both new and 
existing data.


Best regards, Vladimir Yudovin, 

Winguzone - Hosted Cloud Cassandra on Azure and SoftLayer.
Launch your cluster in minutes.



---- On Mon, 17 Oct 2016 11:43:27 -0400Seth Edwards <s...@pubnub.com> wrote ----


We have a few nodes that are running out of disk capacity at the moment and 
instead of adding more nodes to the cluster, we would like to add another disk 
to the server and add it to the list of data directories. My question, is, will 
Cassandra use the new disk for compactions on sstables that already exist in 
the primary directory? 








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