On 07/06/2010 11:17 AM, Pete Zaitcev wrote:
On Tue, 6 Jul 2010 03:24:29 -0400
Jeff Garzik<j...@garzik.org>  wrote:

The following patch, against current hail.git, adds the "CP" command to
chunkd, permitting copying from object->object inside a single table.

What is it for?

Here's a real-world example.

Quoting from the S3 documentation, this describes the "PUT (copy)" operation, something that tabled does not yet support, but should:

        This implementation of the PUT operation creates a copy of an
        object that is already stored in Amazon S3. A PUT copy
        operation is the same as performing a GET and then a PUT.
        Adding the request header, x-amz-copy-source, makes the PUT
        operation copy the source object into the destination bucket.

Assuming that a given tabled object is already fully replicated -- HOPEFULLY the common case for us -- the least expensive way to implement this is

        for each chunkd containing object OLD_KEY

                CHO_CP(object OLD_KEY -> object NEW_KEY)

Assuming each chunkd node has the necessary free space, this method totally avoids using network bandwidth, when creating a copy of an object

        Jeff



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