From: "Russ Cox" <rsc@swtch.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] venti block score & type
Date: Thu, 11 Dec 2003 22:15:18 -0500 [thread overview]
Message-ID: <E1AUdlw-0000Ex-22@t40.swtch.com> (raw)
In-Reply-To: Your message of "Thu, 11 Dec 2003 17:22:10 PST." <09d601c3c04e$5e09aba0$6739a8c0@hpn5415>
> Am I write in assuming that both the score and type have to match for a
> successful venti block read?
Yes.
> 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.
Russ
next prev parent reply other threads:[~2003-12-12 3:15 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 [this message]
2003-12-12 4:05 ` John E. Barham
2003-12-12 4:25 ` Russ Cox
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