Re: Unravelling the mysteries of F_PREALLOCATE (about holes)
Re: Unravelling the mysteries of F_PREALLOCATE (about holes)
- Subject: Re: Unravelling the mysteries of F_PREALLOCATE (about holes)
- From: James Bucanek <email@hidden>
- Date: Fri, 15 Dec 2017 09:36:27 -0700
Changing the subject, because this is really a separate question...
Dominic Giampaolo <mailto:email@hidden>
December 14, 2017 at 9:17 AM
Finally, I've got some new questions as I explore using "holes" and sparse files.
Specifically, if I punch a "hole" in a files with F_PUNCHHOLE, can I later use
F_PREALLOCATE to re-allocate those blocks before I write into them?
No. Just write real data to the hole and apfs will handle allocating blocks
for it. You don't have to worry about that.
I understand that the filesystem will handle allocating the blocks, just
as I understand writing past the EOF will allocate more blocks.
What I'm asking is that, before I start filling a hole, can I
preallocate the space for that hole so I won't be surprised by a disk
full error in the middle of filling it (and to optimize the allocation
of that space)?
Or, said another way, and probably an easier question to answer: Do the
blocks used to satisfy writing into holes come from the same pool of
preallocated blocks?
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