linux-ext4 - RE: planning general storage capacity for y fs

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Message-ID: <007201d080bf$96a0e4e0$c3e2aea0$@codeaurora.org>
Date:	Mon, 27 Apr 2015 10:55:51 +0300
From:	"Dolev Raviv" <draviv@...eaurora.org>
To:	"'Richard Weinberger'" <richard.weinberger@...il.com>
Cc:	<linux-mtd@...ts.infradead.org>, <linux-ext4@...r.kernel.org>,
	"'Tanya Brokhman'" <tlinder@...eaurora.org>
Subject: RE: planning general storage capacity for y fs

>On Sun, Apr 26, 2015 at 1:14 PM, Dolev Raviv <draviv@...eaurora.org> wrote:
>> Hi,
>> I'm looking for guidelines for planning storage capacity. I understand 
>> it strongly depended on the usage type.
>> I want to know at what point storage fullness is effecting performance 
>> in a standard read/write partition. Do different File Systems 
>> (UBIFS/EXT4) have different full-free ratio?
>> What about read only fs? Can I plan less free space in such cases?
>>
>> I'll appreciate any input on this, for UBIFS specific and fs in general.
>
>Not sure if I got your question.
>You want to know how filesystems in general behave when they run out of free space?
>The general answer is that they need more effort to find free space.
>
>In case of UBIFS you also have to think of the garbage collector.
>See http://www.linux-mtd.infradead.org/doc/ubifs.html
>At the end of the day you'll have to run benchmarks on your own to find out how a specific filesystem behaves on your workload...
>

Thanks Richard!
Let me rephrase the question: In the past I knew there was a rule of thumb, 'leave free 30% of the storage space'. Nowadays I couldn't find any reference to this.
I was wondering, is there a known point in UBIFS (or ext4), where leaving less free storage space, that performance is dropping? Maybe a ratio of free-occupied is not the right way to look at it, but to leave a certain size free (e.g. 50MB)?

Thanks,
Dolev
-- 
Qualcomm Israel, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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