UBIFS space consumption

UBIFS space consumption

[Vikram Narayanan]

I am using UBIFS with the below partitioning layout.

<6m(bootloader)
512k(environment)
512k(redundant-environment)
5m(kernel),
170m(filesystem),
40m(user_data1),
-(user_data2)>

For the UBI volume 0 which has 170 MiB,
ubinfo reports 164.7 MiB, which is explained by:

(PEB size - LEB size) * (no of PEB's - reserved PEBs)
(256 - 248) * (680 - 6) = 5.392 MiB
Total size = 170 MiB - 5.39 = 164.6 MiB


root@BOX:/# ubinfo /dev/ubi0
ubi0
Volumes count:                           1
Logical eraseblock size:                 253952 bytes, 248.0 KiB
Total amount of logical eraseblocks:     680 (172687360 bytes, 164.7 MiB)
Amount of available logical eraseblocks: 0 (0 bytes)
Maximum count of volumes                 128
Count of bad physical eraseblocks:       0
Count of reserved physical eraseblocks:  6
Current maximum erase counter value:     5
Minimum input/output unit size:          4096 bytes
Character device major/minor:            253:0
Present volumes:                         0

But according to "df",  UBI volume 0 is sized 148.9 MiB. That's, 15.8 
MiB more in terms of consumption.

root@BOX:/# df -h
Filesystem                Size      Used Available Use% Mounted on
ubi0:rootfs             148.9M    132.8M     16.1M  89% /
root@BOX:/#

Can someone explain where this 15 MiB is getting lost?

Regards,
Vikram

Re: UBIFS space consumption

[Vikram Narayanan]

On 1/18/2013 10:25 PM, Vikram Narayanan wrote:
> I am using UBIFS with the below partitioning layout.
>
> <6m(bootloader)
> 512k(environment)
> 512k(redundant-environment)
> 5m(kernel),
> 170m(filesystem),
> 40m(user_data1),
> -(user_data2)>
>
> For the UBI volume 0 which has 170 MiB,
> ubinfo reports 164.7 MiB, which is explained by:
>
> (PEB size - LEB size) * (no of PEB's - reserved PEBs)
> (256 - 248) * (680 - 6) = 5.392 MiB
> Total size = 170 MiB - 5.39 = 164.6 MiB
>
>
> root@BOX:/# ubinfo /dev/ubi0
> ubi0
> Volumes count:                           1
> Logical eraseblock size:                 253952 bytes, 248.0 KiB
> Total amount of logical eraseblocks:     680 (172687360 bytes, 164.7 MiB)
> Amount of available logical eraseblocks: 0 (0 bytes)
> Maximum count of volumes                 128
> Count of bad physical eraseblocks:       0
> Count of reserved physical eraseblocks:  6
> Current maximum erase counter value:     5
> Minimum input/output unit size:          4096 bytes
> Character device major/minor:            253:0
> Present volumes:                         0
>
> But according to "df",  UBI volume 0 is sized 148.9 MiB. That's, 15.8
> MiB more in terms of consumption.
>
> root@BOX:/# df -h
> Filesystem                Size      Used Available Use% Mounted on
> ubi0:rootfs             148.9M    132.8M     16.1M  89% /
> root@BOX:/#
>
> Can someone explain where this 15 MiB is getting lost?

Artem, Any ideas on this?

Thanks,
Vikram

Re: UBIFS space consumption

[Artem Bityutskiy]

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On Fri, 2013-01-18 at 22:25 +0530, Vikram Narayanan wrote:
> But according to "df",  UBI volume 0 is sized 148.9 MiB. That's, 15.8 
> MiB more in terms of consumption.

Df is not accurate with UBIFS by design, this is covered by this FAQ
entry:

http://www.linux-mtd.infradead.org/faq/ubifs.html#L_df_report

-- 
Best Regards,
Artem Bityutskiy

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Re: UBIFS space consumption

[Vikram Narayanan]

On 2/4/2013 12:33 PM, Artem Bityutskiy wrote:
> On Fri, 2013-01-18 at 22:25 +0530, Vikram Narayanan wrote:
>> But according to "df",  UBI volume 0 is sized 148.9 MiB. That's, 15.8
>> MiB more in terms of consumption.
>
> Df is not accurate with UBIFS by design, this is covered by this FAQ
> entry:
>
> http://www.linux-mtd.infradead.org/faq/ubifs.html#L_df_report
>

Sorry, I think you've mistaken my question. I've referred the above FAQ 
before framing this mail.

The above FAQ explains why the _free_ space shown by 'df' isn't 
accurate. I'm concerned here about the _total_ size shown to me by df, 
which is less than what is reported by ubinfo.

Thanks,
Vikram

Re: UBIFS space consumption

[Artem Bityutskiy]

On Mon, 2013-02-04 at 22:59 +0530, Vikram Narayanan wrote:
> On 2/4/2013 12:33 PM, Artem Bityutskiy wrote:
> > On Fri, 2013-01-18 at 22:25 +0530, Vikram Narayanan wrote:
> >> But according to "df",  UBI volume 0 is sized 148.9 MiB. That's, 15.8
> >> MiB more in terms of consumption.
> >
> > Df is not accurate with UBIFS by design, this is covered by this FAQ
> > entry:
> >
> > http://www.linux-mtd.infradead.org/faq/ubifs.html#L_df_report
> >
> 
> Sorry, I think you've mistaken my question. I've referred the above FAQ 
> before framing this mail.
> 
> The above FAQ explains why the _free_ space shown by 'df' isn't 
> accurate. I'm concerned here about the _total_ size shown to me by df, 
> which is less than what is reported by ubinfo.

I guess dmesg output may give some clue - probably that space is spent
for the journal, orphans area, and indexing area.

-- 
Best Regards,
Artem Bityutskiy