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How do I determine the block size of an ext3 partition on Linux?

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up vote 49 down vote accepted
# tune2fs -l /dev/sda1 | grep -i 'block size'
Block size:               1024

Replace /dev/sda1 with the partition you want to check.

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dumpe2fs -h /dev/md2

will output something with:

Block size:               4096
Fragment size:            4096
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On x86, a filesystem block is just about always 4KiB - the default size - and never larger than the size of a memory page (which is 4KiB).

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This is the same on every platform, the largest block size is supported by ext2/3 is 4096 bytes. – Dave Cheney Jun 23 '09 at 10:06
Thanks Dave! I learned something today ;-) I originally thought the ext3 blocksize could be 8k on platforms that supported 8k memory pages. – wzzrd Jun 23 '09 at 12:44
Wikipedia says it can be 8k: – dfrankow Apr 25 '12 at 22:41
@dfrankow: if you have 8k memory pages, such as on Alpha hardware, yes. But you do not have those on x86 hardware and that is what I was talking about. – wzzrd Apr 26 '12 at 8:03

In the case where you don't have the right to run tune2fs on a device (e.g. in a corporate environment) you can try writing a single byte to a file on the partition in question and check the disk usage:

echo 1 > test
du -h test
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Without root access one can do:

stat -f .

This will give a short info about the filesystem in current directory, including its block size (after Block size:).

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dumpe2fs |grep Block

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stat <<Filename>>

will also give file size in blocks

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