On 14/01/20 09:45, Gionatan Danti wrote:
On 13/01/20 19:09, Darrick J. Wong wrote:
xfs_io -c 'bmap -c -e -l -p -v <whatever>' test.img
Ok, good to know. Thanks.
Hi all, I have an additional question about extszinherit/extsize.
If I understand it correctly, by default it is 0: any non-EOF writes on
a sparse file will allocate how much space it needs. If these writes are
random and small enough (ie: 4k random writes), a subsequent sequential
read of the same file will have much lower performance (because
sequential IO are transformed in random accesses by the logical/physical
block remapping).
Setting a 128K extszinherit (for the entire filesystem) or extsize (for
a file/dir) will markedly improve the situation, as much bigger
contiguous LBA regions can be read for each IO (note: I know SSD and
NVME disks are much less impacted by fragmentation, but I am mainly
speaking about HDD here).
So, my question: there is anything wrong and/or I should be aware when
using a 128K extsize, so setting it the same as cowextsize? The only
possible drawback I can think is a coarse granularity when allocating
from the sparse file (ie: a 4k write will allocate the full 128k extent).
Am I missing something?
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
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