From: "John E. Barham" <jbarham@jbarham.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] venti block score & type
Date: Thu, 11 Dec 2003 20:05:10 -0800 [thread overview]
Message-ID: <0a2d01c3c065$233128c0$6739a8c0@hpn5415> (raw)
In-Reply-To: <E1AUdlw-0000Ex-22@t40.swtch.com>
> > Similarly, that attempting to write a block whose score is already in
venti,
> > but with a different type, will fail?
>
> No. A new index entry will be written for the new type.
>
> Types are really just to help a little in interpreting the
> data. They're almost purely advisory. (Almost, because
> the answer to your first question is yes.) Since blocks are
> zero-truncated before storing, the zero-length block
> might reasonably be interpreted as a data block or as
> a pointer block of any depth. Similarly, if I store a file
> whose contents are the SHA1 hash of a small file, that
> contents will be stored as data, but storing the small file
> itself would use the same block as a first-level pointer
> block.
So venti stores a list of types written for each score? Thus reading a
block would require that the type be in that list, but writing a block would
add the type to the list if it was not already present?
John
next prev parent reply other threads:[~2003-12-12 4:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-12 1:22 John E. Barham
2003-12-12 3:15 ` Russ Cox
2003-12-12 4:05 ` John E. Barham [this message]
2003-12-12 4:25 ` Russ Cox
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