From: Marat Khalili <mkh@rqc.ru>
To: linux-btrfs@vger.kernel.org
Cc: Henk Slager <eye1tm@gmail.com>, Duncan <1i5t5.duncan@cox.net>,
Hugo Mills <hugo@carfax.org.uk>,
"Austin S. Hemmelgarn" <ahferroin7@gmail.com>,
Henk Slager <eye1tm@gmail.com>, A L <crimsoncottage@gmail.com>
Subject: Re: Is autodefrag recommended? -- re-duplication???
Date: Tue, 5 Sep 2017 17:01:10 +0300 [thread overview]
Message-ID: <82e453bf-ff11-a911-c432-3e0173b223b2@rqc.ru> (raw)
In-Reply-To: <710ec5d1-adbf-4ce5-50a5-8b8266ccb672@rqc.ru>
Dear experts,
At first reaction to just switching autodefrag on was positive, but
mentions of re-duplication are very scary. Main use of BTRFS here is
backup snapshots, so re-duplication would be disastrous.
In order to stick to concrete example, let there be two files, 4KB and
4GB in size, referenced in read-only snapshots 100 times each, and some
4KB of both files are rewritten each night and then another snapshot is
created (let's ignore snapshots deletion here). AFAIU 8KB of additional
space (+metadata) will be allocated each night without autodefrag. With
autodefrag will it be perhaps 4KB+128KB or something much worse?
--
With Best Regards,
Marat Khalili
next prev parent reply other threads:[~2017-09-05 14:01 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
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 ` Marat Khalili [this message]
2017-09-05 14:39 ` Is autodefrag recommended? -- re-duplication??? Hugo Mills
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