[Gluster-users] GlusterFS replication over WAN

Keith Freedman freedman at FreeFormIT.com
Wed Aug 13 21:00:06 UTC 2008

At 01:29 PM 8/13/2008, Collin Douglas wrote:
>How does GlusterFS' AFR translator work over a WAN connection?  I know
>the simple answer is that it depends on the connection what's being
>replicated but I'm interested in understanding how it works in a low
>bandwidth situation.

it works fine from my personal experience.  you can probably move 
data at close to wire speed.  I think you'll have different 
experiences depending on whether or not you're using server or client AFR.
My personal preference is to use server based AFR, only because this 
really simplifies client configuration and when you have multiple 
clients acting on the same data sets, when you set up new clients, if 
they're not AFRing correctly you can get some out of sync data.

>We are building a new storage model for our imaging system in which
>GlusterFS is a candidate.
>Current design ideas consist of a tier 1 storage where our current
>"pipeline" of active files would be stored and operated on.  Once the
>files are in a relative static state, they would be moved to tier 2
>storage.  It's this tier 2 storage that would need WAN replication.  In
>this way we would limit the amount of data somewhat that has to be
>replicated as the pipeline files are in an almost constant state of flux.
>The idea is to have an array on site (let's call it building 1), one
>next door in another building (building 2) and one a few hundred miles
>away.  The local arrays will be connected via Infiniband or fiber and
>the remote one via a 10MB link.
>It seems logical that I would want to replicate from building 1 to
>building 2 and then have another AFR configuration at building 2 to
>replicate to the remote site.  Does this fit best practices for
>GlusterFS or should I use more of a hub and spoke method?

I'm not sure I'm conceptualizing your setup quite right. . if this is 
what you mean:
for live active files that are being worked on, AFR building 1 to 
building 2. Lets call this /active
so the /active filesystem would be an AFR fs using servers in 
building 1 and 2.  your 10MB infiniband should be more than sufficient.

For the completed files to have them replicated, you move them to 
/backup which is a volume afr'ed from building 2 to offsite building 
C.  This is probably over lan speed?  hopefully faster than T1, but 
you're moving smaller amounts of data it should be fine.

Remember AFR is a real time replication, so what you can't have is this:
/active being AFR building 1 to building 2, while also having the 
building 2 server set up to afr /active to building C.

I belive this would cause the files once they get updated on building 
2 to get AFR'ed to building C.   I *think* this would make the afr to 
building 1 as slow as the building C afr, but I'm not positive.

>I am interested to hear what people think.
>Collin Douglas
>Adfitech, Inc
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