From: Liu Bo <bo.li.liu@oracle.com>
To: ching <lsching17@gmail.com>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: enquiry about autodefrag option
Date: Wed, 19 Sep 2012 22:12:35 +0800 [thread overview]
Message-ID: <5059D2D3.3050303@oracle.com> (raw)
In-Reply-To: <5059AC5E.1030003@gmail.com>
On 09/19/2012 07:28 PM, ching wrote:
> can anybody helps?
>
> On 09/17/2012 07:15 PM, ching wrote:
>> I am testing btrfs for long-term storage and backup, and i would like
>> to know more about "autodefrag" option:
>>
>> 1. Will "autodefrag" option benefit ssd?
>>
>> My understanding is:
>>
>> autodrag -> number of extent decrease -> metadata decrease -> a
>> "healthier" filesystem in the long run
>>
>> (P.S. I am aware that autodefrag will introduce extra write I/O)
>>
Yes, your understanding is right, random write workloads will benefit from it.
>> 2. AFAIK, "autodefrag" detects small random writes into files and
>> queues them up for an automatic defrag process, so the filesystem will
>> defragment itself while it's used.
>>
>> If the system reboot/crash/remount-ro, will the autodefrag process
>> continue after resume?
>>
For reboot, autodefrag will be waited to finish during umounting btrfs.
For crash and remount-ro, it won't resume since it is not that necessary and we're all
COWed so that the data is ok.
And autodefrag will only take effect when taking the 'autodefrag' mount option.
thanks,
liubo
>>
>
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next prev parent reply other threads:[~2012-09-19 14:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-17 11:15 enquiry about autodefrag option (resent) ching
2012-09-19 11:28 ` enquiry about autodefrag option ching
2012-09-19 14:12 ` Liu Bo [this message]
2012-09-19 17:39 ` Martin Steigerwald
2012-09-20 14:05 ` David Sterba
2012-09-19 23:36 ` ching
2012-09-20 11:51 ` David Sterba
2012-09-20 21:03 ` ching
2012-09-24 15:50 ` David Sterba
-- strict thread matches above, loose matches on Subject: below --
2012-09-17 6:12 ching lu
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