From: Josef Bacik <jbacik@fb.com>
To: Martin <m_btrfs@ml1.co.uk>, <linux-btrfs@vger.kernel.org>
Subject: Re: What to do about snapshot-aware defrag
Date: Mon, 2 Jun 2014 09:22:01 -0400 [thread overview]
Message-ID: <538C7A79.8070407@fb.com> (raw)
In-Reply-To: <lmav1p$ih7$1@ger.gmane.org>
On 05/30/2014 06:00 PM, Martin wrote:
> OK... I'll jump in...
>
> On 30/05/14 21:43, Josef Bacik wrote:
>> Hello,
>>
>> TL;DR: I want to only do snapshot-aware defrag on inodes in snapshots
>> that haven't changed since the snapshot was taken. Yay or nay (with a
>> reason why for nay)
>
> [...]
>>
>> === Summary and what I need ===
>>
>> Option 1: Only relink inodes that haven't changed since the snapshot was
>> taken.
>>
>> Pros:
>> -Faster
>> -Simpler
>> -Less duplicated code, uses existing functions for tricky operations so
>> less likely to introduce weird bugs.
>>
>> Cons:
>> -Could possibly lost some of the snapshot-awareness of the defrag. If
>> you just touch a file we would not do the relinking and you'd end up
>> with twice the space usage.
> [...]
>
>
> Obvious way to go for fast KISS.
>
>
> One question:
>
> Will option one mean that we always need to mount with noatime or
> read-only to allow snapshot defragging to do anything?
>
Yeah atime would screw this up, I hadn't thought of that. With that
being the case I think the only option is to keep the old behavior, we
don't want to screw up stuff like this just because users used a backup
program on their snapshot and didn't use noatime. Thanks,
Josef
next prev parent reply other threads:[~2014-06-02 13:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-30 20:43 What to do about snapshot-aware defrag Josef Bacik
2014-05-30 22:00 ` Martin
2014-05-31 23:51 ` Brendan Hide
2014-06-01 1:52 ` Duncan
2014-06-02 3:07 ` Mitch Harder
2014-06-02 13:19 ` Josef Bacik
2014-06-02 13:22 ` Josef Bacik [this message]
2014-06-03 23:54 ` Martin
2014-06-04 9:19 ` Erkki Seppala
2014-06-04 13:15 ` Martin
2014-06-04 19:33 ` Chris Murphy
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