Re: [Moosefs-users] Grouping chunk servers

[Alexander A. <akh...@ri...>]

Hi all!

As far as I understand "Location awareness" is not exactly what Ioannis expects.
In scenario when whole POP1 goes down and Metadata server was located in POP1
we have data ambiguity because POP1 may be just disconnected by WAN network failure
and real Metadata server may be alive. So, in this case in POP2 we can't
promote Metalogger to Master role.

wbr
Alexander Akhobadze

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Вы писали 8 сентября 2010 г., 21:44:50:
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According to the roadmap (http://www.moosefs.org/roadmap.html), this is slated for the future:

"Location awareness" of chunkserver - optional file mapping IP_address->location_number.
As a location we understand a rack in which the chunkserver is located.
The system would then be able to optimize some operations
(eg. prefer chunk copy which is located in the same rack). 

----- Original Message -----
From: "Ioannis Aslanidis" <ias...@fl...>
To: moo...@li...
Sent: Wednesday, September 8, 2010 11:37:08 AM
Subject: [Moosefs-users] Grouping chunk servers

Hello,

I am testing out MooseFS for around 50 to 100 TeraBytes of data.

I have been successful to set up the whole environment. It was pretty
quick and easy actually. I was able to replicate with goal=3 and it
worked really nicely.

At this point, there is only one requirement that I was not able to
accomplish. I require to have 3 copies of a certain chunk, but my
storage machines are distributed in two points of presence.

I require that each of the points of presence contains at least one
copy of the chunks. This is fine when you have 3 chunk servers, but it
won't work if you have 6 chunk servers. The scenario is the following:

POP1: 4 chunk servers (need 2 replicas here)
POP2: 2 chunk servers (need 1 replica here)

I need this because if the whole POP1 or the whole POP2 go down, I
need to still be able to access the contents. Writes are normally only
performed in POP1, so there are normally only reads in POP2.

The situation is worse if I add 2 more chunk servers in POP1 and 1
more chunk server in POP2.

Is there a way to somehow tell MooseFS that the 4 chunk servers of
POP1 are in one group and that there should be at least 1 replica in
this group and that the 2 chunk servers of POP2 are in another group
and that there should be at least 1 replica in this group?

Is there any way to accomplish this?

Regards.