[Beowulf] copying big files

Abhishek Kulkarni abbyzcool at gmail.com
Fri Aug 8 12:40:30 PDT 2008


Yes, You might want to take a look at XGET, which is a part of the XCPU
clustering framework (http://www.xcpu.org). It was primarily designed to
transfer boot images (kernel and initrd) across the nodes in a cluster in a
very scalable manner, but it can be used to transfer any big
files/directories across the network.
It creates an ad-hoc tree at runtime wherein a client can also "act as a
server" for the other clients. Boot image distribution for over 1024 nodes
has been done in less than 10 seconds.

More recently, Perceus (http://www.perceus.org) has been using XGET as the
default mechanism for scalable VNFS transfer across nodes and comes bundled
with XCPU modules that makes configuring it a lot easier.

  -- Abhishek


On Fri, Aug 8, 2008 at 9:37 AM, Henning Fehrmann <
henning.fehrmann at aei.mpg.de> wrote:

> Hi everybody,
>
> Coping a big file onto all nodes in a cluster is a rather common problem.
> I would have thought that there might be a standard tool for
> distributing the files in an efficient way. So far, I haven't found one.
>

> Assuming one has a network design which allows non blocking full duplex
> wire-speed connections between N/2 pairs of nodes where N is the number
> of nodes in the cluster. It is basically a non blocking coreswitch.
>
> In this case the following scheme would be convenient and rather simple:
>
> The file is placed on node n1 and one builds a chain of nodes n1 , n2 ....
> nN.
>
> One splits the file into many packages (p1..pM), lets say a fragment fits
> into one TCP package. In the first step n1 transmits the package p1 to node
> n2.
> In the second step n1 transmits the package p2 to n2 and n2 transmits p1 to
> node n3.
>
> The transmission of a single package is fast. The time of passing a
> particular
> package through the whole chain of nodes is short compared with time of the
> entire copying process. E.g., using jumbo frames a package can have the
> size of ca 10kB.
> In Gb network the transmission time of a single package between nodes is
> of the order of 0.1 ms.  Even in a cluster with 1024 nodes it takes
> in an ideal case just 0.1s to pass a package from node n1 through all nodes
> to n1024.
>
> On each node the package is stored and, in the end, one reassembles the
> file.
> For big files (size >> 10Mb) the required time is approximately
> the same as one needs for copying the file between two nodes plus 0.1s.
>
> One needs basically a daemon which handles copying requests and establishes
> the connection to next node in the chain.
>
> Has somebody written such a tool?
>
> Cheers,
> Henning Fehrmann
>
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