[Gluster-users] Explaination needed - Distributed Replicated volume

Kaushal M kshlmster at gmail.com
Wed Sep 25 06:37:13 UTC 2013


On Wed, Sep 25, 2013 at 11:38 AM, Jake G. <dj_dark_junglist at yahoo.com> wrote:
> Thank you for your reply. Still need a bit of clarification.
>
> If I copy a 20GB file to the volume how can i still have 180GB left if the
> file gets copied (mirrored) to both glusterfs servers?
>
> My goal is to be able to have redundancy if one of the servers crashes while
> also being able increase the total amount of available volume space.
>
> Am I thinking about this in the wrong way?

If each brick you used provides 100GB, then you have a total of 400GB.
Since you are using replication with 2 replicas, the gluster volume
will be half that size, 200GB. If you copy a 20GB file to this volume,
means 20GB of space on the volume is used, leaving 180GB on the
volume. But, of the total 400GB you had, you will be using up 40GB as
gluster will make a 2 copies of the file.

>
>
>
> ________________________________
> From: Lalatendu Mohanty <lmohanty at redhat.com>
> To: Jake G. <dj_dark_junglist at yahoo.com>
> Cc: "gluster-users at gluster.org" <gluster-users at gluster.org>
> Sent: Wednesday, September 25, 2013 3:10 PM
> Subject: Re: [Gluster-users] Explaination needed - Distributed Replicated
> volume
>
> On 09/25/2013 10:52 AM, Jake G. wrote:
>
> HI all,
>
> I have created a Distributed Replicated volume across 2 glusterfs servers.
>
> Type: Distributed-Replicate
> Status: Started
> Number of Bricks: 2 x 2 = 4
> Transport-type: tcp
> Bricks:
> Brick1: glusterfs-01:/mnt/glusterfs-data/brick1
> Brick2: glusterfs-02:/mnt/glusterfs-data/brick1
> Brick3: glusterfs-01:/mnt/glusterfs-data/brick2
> Brick4: glusterfs-02:/mnt/glusterfs-data/brick2
>
> If each gluster server gives 100GB to the volume. What is the total size of
> the volume going to be? 200GB?
>
> The available size of the volume will be 200GB. Because you have a 2X2
> replicated volume. This means you have 2 pair of replicas. Brick "Brick1:
> glusterfs-01:/mnt/glusterfs-data/brick1" and "Brick2:
> glusterfs-02:/mnt/glusterfs-data/brick1" are a replica pair and they are
> mirror copy of each other. Effectively you will get 100 GB from these two
> bricks . Similarly from the other pair you will get 100GB.  Total available
> size will be 200GB
>
> Say I copy a 20GB file to the volume. what would my available size be? 180GB
> or 160GB?
>
> If you copy 20GB file, the available size would be 180GB.
>
>
> Is there a command to view available sizes, usage, etc.. perhaps?
>
>
> If you have mounted it on Linux "df" command should help you.
>
> I am a bit confused. Thank you!
>
>
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