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Tailoring btrfs for itty bitty devices?
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vaxbrat
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Joined: 05 Oct 2005
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PostPosted: Tue Mar 25, 2014 4:34 am    Post subject: Tailoring btrfs for itty bitty devices? Reply with quote

BTRFS is famously able to handle filesystems that would give each person on the island of Manhattan a 1tb disk drive. However I decided to see if it could also be useful in replacing aufs3 by using its lzo compression feature in small storage devices. More specifically, I was interested to see whether it could squeeze a passable replacement for the default loadset of a thin client appliance such as one of these:

http://www8.hp.com/us/en/campaigns/thin-client-solutions/t510.html

That's the current product which appears to have either a 2gb or 4gb onboard flash. One of the ones I'm working with which is several years old has an AMD Turion X2 processor and only 1gb of flash running an old version of Debian.

With only a:

Code:
USE="X bindist gtk3 kde libkms mmx qt4 rdesktop spice sse sse2 vnc xa -doc"


an emerge of kdebase-meta, kdeadmin-meta, krdc, synergy, PyQt4 and the virt-viewer with spice support put things over the top at 3gb with /usr/src/linux still in but leaving out /usr/portage. I'm in the process of doing an emerge world in a vm with an autobuild that pulls in just nfs-utils and btrfs-progs for another project, but that appears it will need about 1.5gb.

It would be nice if the plumbing could be told to tailor itself for these small environments....
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kernelOfTruth
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Joined: 20 Dec 2005
Posts: 6108
Location: Vienna, Austria; Germany; hello world :)

PostPosted: Fri Mar 28, 2014 6:14 pm    Post subject: Reply with quote

not sure if I understood correctly:

so the filesystem uses itself too much space ?

try

Quote:
-M, --mixed
Mix data and metadata chunks together for more efficient space
utilization. This feature incurs a performance penalty in
larger filesystems. It is recommended for use with filesystems
of 1 GiB or smaller.



from mkfs.btrfs

and the "single" profile option for metadata and data
_________________
https://github.com/kernelOfTruth/ZFS-for-SystemRescueCD/tree/ZFS-for-SysRescCD-4.9.0
https://github.com/kernelOfTruth/pulseaudio-equalizer-ladspa

Hardcore Gentoo Linux user since 2004 :D
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vaxbrat
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Joined: 05 Oct 2005
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PostPosted: Fri Mar 28, 2014 7:33 pm    Post subject: yep... too much overhead Reply with quote

As you note, the --mixed mode turns on if you make a btrfs on something 1gb or smaller. What I'm finding is the internal data structures that get allocated make the btrfs version take about 3gb when it was only needing 700-800mb or so using the squashfs approach with aufs.
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666threesixes666
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PostPosted: Fri Mar 28, 2014 8:56 pm    Post subject: Reply with quote

i had problems with btrfs on less than 1gb partitions. might be like 256 mb is required at minimum? possibly 512mb? i wrote up some stuff for /boot for the wiki about it but it slipped my mind to post it i think. nope i posted it, 280mb minimum is what i got working.
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Ant P.
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PostPosted: Sat Mar 29, 2014 3:31 pm    Post subject: Reply with quote

You might want to try reiser4, it also has lzo. Btrfs is kind of a statistical outlier (in a bad way) when it comes using disk space efficiently.
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