Re: FSSetForkSize writing massive amounts of data over network?
Re: FSSetForkSize writing massive amounts of data over network?
- Subject: Re: FSSetForkSize writing massive amounts of data over network?
- From: James Bucanek <email@hidden>
- Date: Thu, 3 Feb 2011 17:45:32 -0700
Mark Day <mailto:email@hidden> wrote (Thursday, February 3,
2011 10:16 AM -0800):
On Feb 2, 2011, at 9:39 PM, James Bucanek wrote:
What's really weird (to me) is that the client is the one doing the writing.
In exactly the same configuration, the client OS X system can
determine that the destination AFP file server is capable of
copying files
locally (a feature I use often) and will off-load the entire file duplication
to the server. But it can't figure out that the server supports something as
simple as "set EOF" so it has to write a billion zeros over the network????
The server does support "set EOF", but the protocol doesn't guarantee that the
additional space is zero filled.
That message is coming through loud and clear. :)
It's clear that the behavior of FSSetFileSize has been changed
to guarantee that the newly extended range (or at least the
newly allocated blocks) is filled with zeros, consistent with
BSD's behavior, going so far as to explicitly write data to a
remote file server to ensure that.
This is somewhat distressing, as I have several situations where
I set the EOF and then write to the file. I realize now that, in
many cases, this technique is writing the file twice!
I also realize that there's not much to be done about it now, as
this is obviously a design decision that's been etched in stone.
The actualCount value returned for the network volume is the same as the
requested value, indicating a successful allocation. In my
test case these were values between 100MB and 160GB. In every
test, the free
space reported by the volume remained the same.
That sounds like a bug to me.
I tend to agree.
Thanks for the info.
--
James Bucanek
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