Some preamble: I'm taking bitwise copy of disk devices (via
dd command) from twin hosts (i.e. with the same virtualized hardware layout and software packages, but with different history of usage). To optimize image size I trailed all empty space on partitions with zeroes (e.g. from
/dev/zero). I'm also aware of reserved blocks per partition and temporarily downgraded that value to 0% before trailing.
But I'm curious about discrepancy of the final compressed (by
bzip2) images. All hosts have almost the same
tar-gziped size of files, but compressed
dd images have significant variety (up to 20%). So how could it be? Is there a reason in the filesystem journals data which I was unable to purge? There are over ten partitions on the host and each reported of 128Mb journal size. (I also checked defragmentation, it's all ok: 0 or 1 due to
e4defrag tool report)
So, my question is it possible somehow to clean
ext3/ext4 filesystem journals? (safely for stored data of course :)
I defenitely asked a question about how to clean (purge/refresh) journals in
ext3/ext4 filesystem if possible or maybe I'm mistaken and there is no such feature as reclaiming disk space occupied by filesystem journals, so all solutions are welcome. An intention to ask the question I put as premise into the preamble and the answer to my question would help me to investigate the issue I encountered with.