Mailinglist Archive: opensuse (878 mails)

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Re: [opensuse] Another example of deliberate systemð supporters deliberately sabotaging previously working software...
  • From: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
  • Date: Mon, 3 Aug 2015 13:11:53 -0600
  • Message-id: <CAJCQCtRi5K9_Q7F7tyFWo6WGc4sHeZnJb=Fsz3e7AwHk3G88Sg@mail.gmail.com>
On Mon, Aug 3, 2015 at 12:51 PM, Andrei Borzenkov <arvidjaar@xxxxxxxxx> wrote:
В Mon, 3 Aug 2015 12:33:56 -0600
Chris Murphy <lists@xxxxxxxxxxxxxxxxx> пишет:


Actually it is exactly what CoW is. It is btrfs which is not CoW - more
appropriate name is "redirect on write" or "write anywhere" (which is
how oldest implementation is called).

There is no "copy" involved in btrfs write process.

COW semantically means deduplication,

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means
just what I choose it to mean—neither more nor less."

Please, please - CoW snapshot means - before new data is WRITTEN,
original data is COPIED somewhere else.

No, that's just how LVM thick did it. LVM thin does it differently,
and it's COW.


CoW snapshots have absolutely
nothing to do with deduplication and existed long before deduplication
started to be used in storage world.

You're just thinking of this in terms of the LVM thick implementation,
not the long standing denotation of the term. It was something of an
evil necessity that LVM did it the way it did it, and that's why it
doesn't perform well and will eventually be supplanted by LVM thin
snapshots.




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Chris Murphy
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