Re: [Moosefs-users] Make MooseFS write on a certain node

[Michal B. <mic...@ge...>]

MooseFS operates on 64MB chunks. So at the beginning all copies would be
created on all the nodes. So first 3GB of data (as 1GB is reserved at node1)
would be fully distributed over three nodes. Later the remaining 2GB of data
would be written at node2 and node3. So the file would have 3GB of data in
three copies but the whole 5GB would be only in two copies. All writes would
be successful, the file would be accessible but it would be "undergoal". 

 

When you expand space on node1 or attach node4 the system will automatically
try copy the remaining 2GB of data so that the file has all its data in full
three copies.

 

 

Regards

Michal

 

From: Piotr Skurczak [mailto:pio...@gm...] 
Sent: Thursday, January 13, 2011 5:11 PM
To: Michal Borychowski
Cc: moo...@li...
Subject: Re: [Moosefs-users] Make MooseFS write on a certain node

 

Hello!

 

What if for instance I have different size disks dedicated for moosefs ,
like :

 

node1 : 4 GB

node2 : 7 GB

node3 : 10 GB

 

then,

- what happens if I want to write 5 GB iso file with mfssetgoal = 3 on a
directory ? Will only 2 copies be written to node2 and 3 or will I get an
error saying capacity warning ?

 

- if MFS chooses the nodes randomly then having presented the situation
above then my conclusions on what would happen if I wanted top copy - again
5 GB file are :

1-st option: mfsmaster has chosen node1 and node2 to write the 5 GB file.
There's not enough free space. Copy failed.

2-nd option: mfsmaster has chosen node 2 and node3 - write succeeded.

3-rd option: mfsmaster has chosen node3 and node1 - write fails. 

 

hence there're 33 % chances that I will save my file on the storage.

 

What about this ?  

 

2011/1/13 Michal Borychowski <mic...@ge...>

Hi Piotr!

 

For the moment there is no chunk or rack "awareness". So generally speaking
chunks are chosen by random, the only exception is when the

client is also a chunk.

 

For more detailed information you can have a look at this post:

http://sourceforge.net/mailarchive/message.php?msg_id=26743571 

 

 

If you need any further assistance please let us know.

 

Kind regards

Michał Borychowski 

MooseFS Support Manager

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Gemius S.A.

ul. Wołoska 7, 02-672 Warszawa

Budynek MARS, klatka D

Tel.: +4822 874-41-00

Fax : +4822 874-41-01

 

 

 

 

 

From: Piotr Skurczak [mailto:pio...@gm...] 
Sent: Thursday, January 13, 2011 10:31 AM
To: moo...@li...
Subject: [Moosefs-users] Make MooseFS write on a certain node

 

Hello,  

 

Quick question. Is it possible to force moosefs, to tell it where a copy
should be written ? 

Or - another way - if I copy a testfile.tar.gz (2 MB) to my mountpoint - can
I point on which chunk the data can be written ?

 

My file system is generally a home made high availability samba share with
nodes scattered around the world for files < 5 MB.

If users from a certain location decide to write only one copy it would be
good not to write to a node that is on the other side of the globe, but 5
meters ahead...

 

Peter