From: dexen deVries <dexen.devries-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: how are files allocated on nilfs?
Date: Wed, 4 May 2011 18:02:16 +0200 [thread overview]
Message-ID: <201105041802.17155.dexen.devries@gmail.com> (raw)
Hi,
a possibly naive question: how are files allocated on nilfs?
Asking, because I've expected a large-ish (128MB) file to be mostly
continuous, modulo segment headers. But it doesn't seem so. A small test to
narrow down the question:
0) created a new, empty, nilfs, on a separate partition (about 1GB size)
1) created a file with dd if=/dev/zero of=a.bin bs=$((128*1024*1024)) count=1
2) ran hdparm --fibmap a.bin
output:
byte_offset begin_LBA end_LBA sectors
0 231 16446 16216
8302592 16503 29094 12592
14749696 29239 32830 3592
16588800 32895 49214 16320
24944640 49255 58158 8904
29503488 58327 65598 7272
33226752 65663 81982 16320
41582592 82007 87230 5224
44257280 87415 98366 10952
49864704 98431 114750 16320
58220544 114759 116302 1544
59011072 116503 131134 14632
66502656 131191 145374 14184
73764864 145519 147518 2000
74788864 147583 163902 16320
83144704 163951 174446 10496
88518656 174607 180286 5680
91426816 180351 196670 16320
99782656 196703 203518 6816
103272448 203695 213054 9360
108064768 213119 229438 16320
116420608 229455 232590 3136
118026240 232783 245822 13040
124702720 245887 261662 15776
while the first chunk of file fills almost whole segment, several subsequent
chunks are much smaller than segment. Why is it so?
Regards,
--
dexen deVries
[[[↓][→]]]
``In other news, STFU and hack.''
mahmud, in response to Erann Gat's ``How I lost my faith in Lisp''
http://news.ycombinator.com/item?id=2308816
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next reply other threads:[~2011-05-04 16:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 16:02 dexen deVries [this message]
[not found] ` <201105041802.17155.dexen.devries-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-05-05 1:43 ` how are files allocated on nilfs? Ryusuke Konishi
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