moosefs-users

[Moosefs-users] Local writing and rack awareness?

[Stas O. <sta...@gm...>]

Hi.

I have couple of questions I wanted to ask about MFS:

1) In case the MFS chunk-server writes data, does it recognizes this and
writes to itself first, and also reads from itself first, in order to
speed-up operations?

2) Also, does MFS support rack awareness, where it replicates the files
within same sub-net first, and only moves later to other sub-nets?

Regards.

Re: [Moosefs-users] Local writing and rack awareness?

[Laurent W. <lw...@hy...>]

On Sun, 15 Aug 2010 22:55:15 +0300
Stas Oskin <sta...@gm...> wrote:

> Hi.
> 
> I have couple of questions I wanted to ask about MFS:
> 
> 1) In case the MFS chunk-server writes data, does it recognizes this and
> writes to itself first, and also reads from itself first, in order to
> speed-up operations?
hmmmm. master decides where data are to be written. Chunkservers read
or write data when they are commanded. Chunkservers do not, afaik, take
decisions on their own about read or write.
> 
> 2) Also, does MFS support rack awareness, where it replicates the files
> within same sub-net first, and only moves later to other sub-nets?
I think you're doing a mix-up between rack and subnet. you can
perfectly have the same subnet in several racks.
Anyway, rack awareness is not yet implemented. It's on the todo list as
far as I can remember. (can't verify as I can't access web for now).
Hope it helps,
-- 
Laurent Wandrebeck
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Euratechnologies
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Re: [Moosefs-users] Local writing and rack awareness?

[Stas O. <sta...@gm...>]

Hi.

hmmmm. master decides where data are to be written. Chunkservers read
> or write data when they are commanded. Chunkservers do not, afaik, take
> decisions on their own about read or write.
>


The idea is in case the application running on chunk master, it will write
and read locally for improved performance.

I think you're doing a mix-up between rack and subnet. you can
> perfectly have the same subnet in several racks.
> Anyway, rack awareness is not yet implemented. It's on the todo list as
> far as I can remember. (can't verify as I can't access web for now).
>

You right - this specified on the chunk server level as additional ID.
The idea is to have reads in same rack, but replications across racks. This
increase performance and lowers Intra/Inter net bandwidth usage, while still
providing required level of fault tolerance.


These two features are being implemented in many DFS systems these days, and
I think they will be a great addition to MFS as well.

For example:
http://kosmosfs.sourceforge.net/features.html
"
Rack-aware data placement: The chunk placement algorithm is rack-aware.
Whereever possible, it places chunks on different racks.
.
.
Local read optimization: When applications are run on the same nodes as
chunkservers, the CloudStore client library contains an optimization for
reading data locally. That is, if the chunk is stored on the same node as
the one on which the application is executing, data is read from the local
node.
"

Regards.

Re: [Moosefs-users] Local writing and rack awareness?

[Michał B. <mic...@ge...>]

Hi Stas!

 

Ad. 1)

Yes. When one copy of a chunk is located on a computer from which comes
request to return all locations of the file (both at read and write) then
this locations is sent as first. In case of reading client chooses this
location as a preferred one, in case of writing the location would be at the
first place in a chain of connections.

 

Ad. 2)

No. It is on our roadmap but now we cannot tell when this functionality
would be implemented.

 

If you need to increase performance you can have a look here:
http://www.moosefs.org/moosefs-faq.html#mtu. Link Aggregation really helps.

 

 

Regards

Michal

 

From: Stas Oskin [mailto:sta...@gm...] 
Sent: Sunday, August 15, 2010 9:55 PM
To: moosefs-users
Subject: [Moosefs-users] Local writing and rack awareness?

 

Hi.

I have couple of questions I wanted to ask about MFS:

1) In case the MFS chunk-server writes data, does it recognizes this and
writes to itself first, and also reads from itself first, in order to
speed-up operations?

2) Also, does MFS support rack awareness, where it replicates the files
within same sub-net first, and only moves later to other sub-nets?

Regards.