From: Hugo Mills <hugo@carfax.org.uk>
To: Marat Khalili <mkh@rqc.ru>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Is autodefrag recommended?
Date: Mon, 4 Sep 2017 10:54:44 +0000 [thread overview]
Message-ID: <20170904105444.GA23980@carfax.org.uk> (raw)
In-Reply-To: <710ec5d1-adbf-4ce5-50a5-8b8266ccb672@rqc.ru>
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On Mon, Sep 04, 2017 at 12:31:54PM +0300, Marat Khalili wrote:
> Hello list,
> good time of the day,
>
> More than once I see mentioned in this list that autodefrag option
> solves problems with no apparent drawbacks, but it's not the
> default. Can you recommend to just switch it on indiscriminately on
> all installations?
>
> I'm currently on kernel 4.4, can switch to 4.10 if necessary (it's
> Ubuntu that gives us this strange choice, no idea why it's not 4.9).
> Only spinning rust here, no SSDs.
autodefrag effectively works by taking a small region around every
write or cluster of writes and making that into a stand-alone extent.
This has two consequences:
- You end up duplicating more data than is strictly necessary. This
is, IIRC, something like 128 KiB for a write.
- There's an I/O overhead for enabling autodefrag, because it's
increasing the amount of data written.
Hugo.
--
Hugo Mills | The future isn't what it used to be.
hugo@... carfax.org.uk |
http://carfax.org.uk/ |
PGP: E2AB1DE4 |
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next prev parent reply other threads:[~2017-09-04 10:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 9:31 Is autodefrag recommended? Marat Khalili
2017-09-04 10:23 ` Henk Slager
2017-09-04 10:34 ` Duncan
2017-09-04 11:09 ` Henk Slager
2017-09-04 22:27 ` Duncan
2017-09-04 10:54 ` Hugo Mills [this message]
2017-09-05 11:45 ` Austin S. Hemmelgarn
2017-09-05 12:49 ` Henk Slager
2017-09-05 13:00 ` Austin S. Hemmelgarn
2017-09-05 12:36 ` A L
2017-09-05 14:01 ` Is autodefrag recommended? -- re-duplication??? Marat Khalili
2017-09-05 14:39 ` Hugo Mills
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