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From Ryan Svihla <rsvi...@datastax.com>
Subject Re: Replacing nodes disks
Date Sun, 21 Dec 2014 15:14:40 GMT
Cassandra is designed to rebuild a node from other nodes, whether a node is
dead by your hand because you killed it or fate is irrelevant, the process
is the same, a "new node" can be the same hostname and ip or it can have
totally different ones.

On Sun, Dec 21, 2014 at 6:01 AM, Or Sher <or.sher1@gmail.com> wrote:
>
> If I'll use the replace_address parameter with the same IP address, would
> that do the job?
>
> On Sun, Dec 21, 2014 at 11:20 AM, Or Sher <or.sher1@gmail.com> wrote:
>
>> What I want to do is kind of replacing a dead node -
>> http://www.datastax.com/documentation/cassandra/2.0/cassandra/operations/ops_replace_node_t.html
>> But replacing it with a clean node with the same IP and hostname.
>>
>> On Sun, Dec 21, 2014 at 9:53 AM, Or Sher <or.sher1@gmail.com> wrote:
>>
>>> Thanks guys.
>>> I have to replace all data disks, so I don't have another large enough
>>> local disk to move the data to.
>>> If I'll have no choice, I will backup the data before on some other node
>>> or something, but I'd like to avoid it.
>>> I would really love letting Cassandra do it thing and rebuild itself.
>>> Did anybody handled such cases that way (Letting Cassandra rebuild it's
>>> data?)
>>> Although there are no documented procedure for it, It should be possible
>>> right?
>>>
>>> On Fri, Dec 19, 2014 at 8:41 AM, Jan Kesten <j.kesten@enercast.de>
>>> wrote:
>>>
>>>> Hi Or,
>>>>
>>>> I did some sort of this a while ago. If your machines do have a free
>>>> disk slot - just put another disk there and use it as another
>>>> data_file_directory.
>>>>
>>>> If not - as in my case:
>>>>
>>>> - grab an usb dock for disks
>>>> - put the new one in there, plug in, format, mount to /mnt etc.
>>>> - I did an online rsync from /var/lib/cassandra/data to /mnt
>>>> - after that, bring cassandra down
>>>> - do another rsync from /var/lib/cassandra/data to /mnt (should be
>>>> faster, as sstables do not change, minimizes downtime)
>>>> - if you need adjust /etc/fstab if needed
>>>> - shutdown the node
>>>> - swap disks
>>>> - power on the node
>>>> - everything should be fine ;-)
>>>>
>>>> Of course you will need a replication factor > 1 for this to work ;-)
>>>>
>>>> Just my 2 cents,
>>>> Jan
>>>>
>>>> rsync the full contents there,
>>>>
>>>> Am 18.12.2014 um 16:17 schrieb Or Sher:
>>>>
>>>>  Hi all,
>>>>>
>>>>> We have a situation where some of our nodes have smaller disks and we
>>>>> would like to align all nodes by replacing the smaller disks to bigger
ones
>>>>> without replacing nodes.
>>>>> We don't have enough space to put data on / disk and copy it back to
>>>>> the bigger disks so we would like to rebuild the nodes data from other
>>>>> replicas.
>>>>>
>>>>> What do you think should be the procedure here?
>>>>>
>>>>> I'm guessing it should be something like this but I'm pretty sure it's
>>>>> not enough.
>>>>> 1. shutdown C* node and server.
>>>>> 2. replace disks + create the same vg lv etc.
>>>>> 3. start C* (Normally?)
>>>>> 4. nodetool repair/rebuild?
>>>>> *I think I might get some consistency issues for use cases relying on
>>>>> Quorum reads and writes for strong consistency.
>>>>> What do you say?
>>>>>
>>>>> Another question is (and I know it depends on many factors but I'd
>>>>> like to hear an experienced estimation): How much time would take to
>>>>> rebuild a 250G data node?
>>>>>
>>>>> Thanks in advance,
>>>>> Or.
>>>>>
>>>>> --
>>>>> Or Sher
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Or Sher
>>>
>>
>>
>>
>> --
>> Or Sher
>>
>
>
>
> --
> Or Sher
>


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Ryan Svihla

Solution Architect

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