On 16/05/15 21:31, Jacco Ligthart wrote:
On 05/16/2015 04:18 PM, Gordan Bobic wrote:
Hi all,
I have been mulling over an idea and wanted to run it past people here
to see if there are any strong opinions either way. Speifically, where
images are provided, I've been pondering making the based on zfs
(zfs-fuse for now, at least until kernel mode zfs is more tested.
Yes, I am catually proposing/advocating using zfs even for the rootfs.
I have been using nothing but zfs for all my non-root block devices
for years now, and have been using it for my rootfs-es wherever
possible since late last year without any problems. And zfs is one of
those things that once you try it you simply cannot imagine how you
ever managed to make do without it.
There is certainly a fair amount of work involved in producing images,
and most importantly kernels and initramfs-es to go with those images,
but I think the benefits are worth it (where the kernel available for
the devices supports at least fuse or at least the kernel sources are
available.
The main drawback is performance. zfs-fuse is going to be slower than
ext*, there's no two ways about it. This is certainly going to be
noticeable for those running with SSDs. It may not be particularly
noticeable for those running on spinning rust but it will use more
CPU, and the zfs ARC cache will not be treated as releasable like
normal page cache under memory pressure (so have swap if you this is a
problem).
Thoughts?
I also recently thought about other filesystems for the images, but my
options were xfs (to align with upstream) or one of the FS-es that
supposedly work better for SD-cards (yaffs? f2fs? ubifs?).
I'm not sure how much difference most of those really make. I saw good
performance with nilfs2, but focusing on performance to the exclusion of
everything else is, IMO, ill advised.
But, as the pi normally boots without an initrd (which I like) and
adjusting it to have an initrd seems non-trivial (according to google) I
decided to leave it at ext4.
How is it non-trivial? What boot loader does it use? U-boot handles this
reasonably gracefully.
Things I'm still considering are nodiratime and data=writeback for ext4.
Is fiddling with FS options really that advantageous over letting the
user just configure it the way they want, including picking the FS they
want themselves?
Gordan
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