Ext2/3 Filesystem Analysis
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From: Yedire, Sandeep on 9 Jun 2010 05:50 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Alan Cox on 9 Jun 2010 05:50 > 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Andi Kleen on 9 Jun 2010 08:10
Alan Cox <alan(a)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(a)linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |