On Tue, Oct 30, 2012 at 5:47 PM, ching [off-list ref] wrote:

On 10/31/2012 06:19 AM, Hugo Mills wrote:

quoted

On Tue, Oct 30, 2012 at 10:14:12PM +0000, Hugo Mills wrote:

quoted

On Wed, Oct 31, 2012 at 05:40:25AM +0800, ching wrote:

quoted

On 10/30/2012 08:17 PM, cwillu wrote:

quoted

quoted

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If there is a lot of small files, then the size of metadata will be
undesirable due to deduplication

Yes, that is a fact, but if that really matters depends on the use-case
(e.g., the small files to large files ratio, ...). But as btrfs is designed
explicitly as a general purpose file system, you usually want the good
performance instead of the better disk-usage (especially as disk space isn't
expensive anymore).

As I understand it, in basically all cases the total storage used by
inlining will be _smaller_, as the allocation doesn't need to be
aligned to the sector size.

if i have 10G small files in total, then it will consume 20G by default.

   If those small files are each 128 bytes in size, then you have
approximately 80 million of them, and they'd take up 80 million pages,
or 320 GiB of total disk space.

   Sorry, to make that clear -- I meant if they were stored in Data.
If they're inlined in metadata, then they'll take approximately 20 GiB
as you claim, which is a lot less than the 320 GiB they'd be if
they're not.

   Hugo.

is it the same for:
1. 3k per file with leaf size=4K
2. 60k per file with leaf size=64k

import os
import sys

data = "1" * 1024 * 3

for x in xrange(100 * 1000):
  with open('%s/%s' % (sys.argv[1], x), 'a') as f:
    f.write(data)

root@repository:~$ mount -o loop ~/inline /mnt
root@repository:~$ mount -o loop,max_inline=0 ~/noninline /mnt2

root@repository:~$ time python test.py /mnt
real	0m11.105s
user	0m1.328s
sys	0m5.416s
root@repository:~$ time python test.py /mnt2
real	0m21.905s
user	0m1.292s
sys	0m5.460s

root@repository:/$ btrfs fi df /mnt
Data: total=1.01GB, used=256.00KB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=652.70MB
Metadata: total=8.00MB, used=0.00

root@repository:/$ btrfs fi df /mnt2
Data: total=1.01GB, used=391.12MB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=60.98MB
Metadata: total=8.00MB, used=0.00

3k data, 4k leaf: inline is twice the speed, but 1.4x bigger.

----

root@repository:~$ mkfs.btrfs inline -l 64k
root@repository:~$ mkfs.btrfs noninline -l 64k
...
root@repository:~$ time python test.py /mnt
real	0m12.244s
user	0m1.396s
sys	0m8.101s
root@repository:~$ time python test.py /mnt2
real	0m13.047s
user	0m1.436s
sys	0m7.772s

root@repository:/$ btr\fs fi df /mnt
Data: total=8.00MB, used=256.00KB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=342.06MB
Metadata: total=8.00MB, used=0.00

root@repository:/$ btr\fs fi df /mnt2
Data: total=1.01GB, used=391.10MB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=50.06MB
Metadata: total=8.00MB, used=0.00

3k data, 64k leaf: inline is still 10% faster, and is now 25% smaller

----

data = "1" * 1024 * 32

... (mkfs, mount, etc)

root@repository:~$ time python test.py /mnt
real	0m17.834s
user	0m1.224s
sys	0m4.772s
root@repository:~$ time python test.py /mnt2
real	0m20.521s
user	0m1.304s
sys	0m6.344s

root@repository:/$ btrfs fi df /mnt
Data: total=4.01GB, used=3.05GB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=54.00MB
Metadata: total=8.00MB, used=0.00

root@repository:/$ btrfs fi df /mnt2
Data: total=4.01GB, used=3.05GB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=53.56MB
Metadata: total=8.00MB, used=0.00

32k data, 64k leaf: inline is still 10% faster, and is now the same
size (not dead sure why, probably some interaction with the size of
the actual write that happens)

----

data = "1" * 1024 * 7

... etc


root@repository:~$ time python test.py /mnt
real	0m9.628s
user	0m1.368s
sys	0m4.188s
root@repository:~$ time python test.py /mnt2
real	0m13.455s
user	0m1.608s
sys	0m7.884s

root@repository:/$ btrfs fi df /mnt
Data: total=3.01GB, used=1.91GB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=74.69MB
Metadata: total=8.00MB, used=0.00

root@repository:/$ btrfs fi df /mnt2
Data: total=3.01GB, used=1.91GB
System, DUP: total=8.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=74.69MB
Metadata: total=8.00MB, used=0.00

7k data, 64k leaf:  30% faster, same data usage.

----

Are we done yet?  Can I go home now? ;p