[Sheepdog] Sheepdog cluster expansion

Fernando Frediani (Qube) fernando.frediani at qubenet.net
Mon Aug 1 16:46:20 CEST 2011

Hi Kazutaka,

So if eventually I add a new node which doesn't have the same size as the others (say 5TB) the maximum data to be stored will be 8.3TB per node ? If so than I risk my 5TB node run out of space ? Or 5TB will be the limit of data that I will be able to store on each of my 10TB nodes ?
I mean in short what happens or what are my limits with a 3 nodes configuration 10TB+10TB+5TB.

I guess I workaround for this is run a sheepdog process for each disk, but that would be fairly more complex and eventually use more Ram memory ? Thinking about a server with 24 disks.
What you suggest in a scenario like this ?

For the last question I think it is somehow related to the first one. If eventually I add a node with enough disks for the OS+KVM and some small storage(say 2 disks, so 500GB) just to run the run the sheepdog process I would run in a worst scenario as described below ?



-----Original Message-----
From: MORITA Kazutaka [mailto:morita.kazutaka at lab.ntt.co.jp] 
Sent: 01 August 2011 13:44
To: Fernando Frediani (Qube)
Cc: 'sheepdog at lists.wpkg.org'
Subject: Re: [Sheepdog] Sheepdog cluster expansion

At Mon, 1 Aug 2011 08:44:15 +0000,
Fernando Frediani (Qube) wrote:
> Hi,
> If I start my cluster with the following scenario: 2 Servers with 10TB each (one single logic drive presented by the Raid controller) and obviously copies=2 how should I grow it ?
> Should I always add a 2 x Servers of 10TB every time I need to increase my storage or can I just do one by one and it will always balance the data between any number of servers available ?

You can add one by one.  The data will be balanced automatically without any configuration.

> If I can add one by one does these servers need always to be the exactly same size of others (10TB) or there is some flexibility on having a mixture of that and again the things will balance fine ?

Sheepdog assumes that all the disks have the same free space, so the data will be balanced uniformly even if there is a much larger disk.
It is not impossible to handle different sized disks, but it is one of the future works.

> In another slightly different scenario if I have already enough storage for my KVM Virtual Machines and all I need is just CPU and Memory is it OK jus to add a node with that but without storage and make it use the sheepdog for its VMs as well ?

Basically, Sheepdog needs a local disk to use for a storage system.
Though your VMs can connect to the other machine from out side of Sheepdog, in that case the connected server (gateway) could be a single point of failure.  The connection failover is also one of TODO items.



More information about the sheepdog mailing list