* Ext2/3 Filesystem Analysis
@ 2010-06-09 9:41 Yedire, Sandeep
2010-06-09 9:58 ` Alan Cox
0 siblings, 1 reply; 3+ messages in thread
From: Yedire, Sandeep @ 2010-06-09 9:41 UTC (permalink / raw)
To: linux-kernel
Hi All,
I am currently working on Ext2/3 filesystem analysis on SLC NAND Flash device.
I have added code at driver level to note the erase and write count to
each sectors at NAND flash device.
With test application doing read/write of 64MB file with a particular
pattern, I have noted below results
With Ext2:
Filesystem block at Sector 0 is being updated more frequently at ratio
of 4 to 4.5 times that of data block.
Filesystem block(super block copies) are being updated at twice the
frequency compared to data block.
With Ext3:
Filesystem block at Sector 0 is being updated more frequently at ratio
of 5.5 to 6 times that of data block.
Filesystem block(super block copies) are being updated at around
1.5times the frequency compared to data block.
Has anyone come across this kind of behaviour with these filesystems
on NAND Flash?
Please comment on this results.
Many thanks,
Sandeep
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Ext2/3 Filesystem Analysis
2010-06-09 9:41 Ext2/3 Filesystem Analysis Yedire, Sandeep
@ 2010-06-09 9:58 ` Alan Cox
2010-06-09 12:06 ` Andi Kleen
0 siblings, 1 reply; 3+ messages in thread
From: Alan Cox @ 2010-06-09 9:58 UTC (permalink / raw)
To: Yedire, Sandeep; +Cc: linux-kernel
> With Ext3:
> Filesystem block at Sector 0 is being updated more frequently at ratio
> of 5.5 to 6 times that of data block.
> Filesystem block(super block copies) are being updated at around
> 1.5times the frequency compared to data block.
>
> Has anyone come across this kind of behaviour with these filesystems
> on NAND Flash?
ext2/3 are not intended to be used with flash - they do not wear level,
in fact the journal and some other blocks will get very heavily used
compared to other blocks.
See the MTD drivers and related file systems/mapping layers (UBIFS etc)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Ext2/3 Filesystem Analysis
2010-06-09 9:58 ` Alan Cox
@ 2010-06-09 12:06 ` Andi Kleen
0 siblings, 0 replies; 3+ messages in thread
From: Andi Kleen @ 2010-06-09 12:06 UTC (permalink / raw)
To: Alan Cox; +Cc: Yedire, Sandeep, linux-kernel
Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
>> With Ext3:
>> Filesystem block at Sector 0 is being updated more frequently at ratio
>> of 5.5 to 6 times that of data block.
>> Filesystem block(super block copies) are being updated at around
>> 1.5times the frequency compared to data block.
>>
>> Has anyone come across this kind of behaviour with these filesystems
>> on NAND Flash?
>
> ext2/3 are not intended to be used with flash - they do not wear level,
Or rather not intended to be used with flash that does not have
an own wear level layer.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2010-06-09 9:41 Ext2/3 Filesystem Analysis Yedire, Sandeep
2010-06-09 9:58 ` Alan Cox
2010-06-09 12:06 ` Andi Kleen
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