planning general storage capacity for y fs

planning general storage capacity for y fs

[Dolev Raviv]

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.

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

Re: planning general storage capacity for y fs

[Richard Weinberger]

On Sun, Apr 26, 2015 at 1:14 PM, Dolev Raviv <draviv@codeaurora.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

RE: planning general storage capacity for y fs

[Dolev Raviv]

>On Sun, Apr 26, 2015 at 1:14 PM, Dolev Raviv <draviv@codeaurora.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

Re: planning general storage capacity for y fs

[Richard Weinberger]

Am 27.04.2015 um 09:55 schrieb Dolev Raviv:
> 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.

Most likely because this is and was always kind of superstition. ;)
An almost full filesystems has to do more to find free space, but I don't dare to
give rules of thumb.

> 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)?

I don't think so. Maybe Ted can give you more details on ext4.
For UBIFS I'd say, figure yourself. i.e. run benchmarks...

Thanks,
//richard