On 2016-09-11 15:21, Martin Steigerwald wrote:
Am Sonntag, 11. September 2016, 21:56:07 CEST schrieb Imran Geriskovan:
On 9/11/16, Duncan <1i5t5.dun...@cox.net> wrote:
Martin Steigerwald posted on Sun, 11 Sep 2016 17:32:44 +0200 as excerpted:
What is the smallest recommended fs size for btrfs?
Can we say size should be in multiples of 64MB?
Do you want to know the smalled *recommended* or the smallest *possible*
size?
In fact both.
I'm reconsidering my options for /boot
Well my stance on boot still is: Ext4. Done.
:)
It just does not bother me. It practically makes no difference at all. It has
no visible effect on my user experience and I never saw the need to snapshot /
boot.
FWIW, I use BTRFS for /boot, but it's not for snapshotting or even the
COW, it's for DUP mode and the error recovery it provides. Most people
don't think about this if it hasn't happened to them, but if you get a
bad read from /boot when loading the kernel or initrd, it can
essentially nuke your whole system. I run BTRFS for /boot in DUP mode
with mixed-bg (because I only use 512MB for boot) to mitigate the chance
that a failed read has any impact, and ensure that if it does, it will
refuse to boot instead of booting with a corrupted kernel or initrd.
But another approach in case you want to use BTRFS for /boot is to use a
subvolume. Thats IMHO the SLES 12 default setup. They basically create
subvolumes for /boot, /var, /var/lib/mysql – you name it. Big advantage: You
have one big FS and do not need to plan space for partitions or LVs.
Disadvantage: If it breaks, it breaks.
That said, I think at a new installation I may do this for /boot. Just put it
inside a subvolume.
From my experiences at work with customer systems and even some systems I
setup myself, I often do not use little partitions anymore. I did so for a
CentOS 7 training VM, just 2 GiB XFS for /var. Guess what happened? Last
update was too long ago, so… yum tried to download a ton of packages and then
complained it has not enough space in /var. Luckily I used LVM, so I enlarged
partition LVM resides on, enlarged PV and then enlarged /var. There may be
valid reasons to split things up, and I am quite comfortable with splitting /
boot out, cause its, well, plannable easily enough. And it may make sense to
split /var or /var/log out. But on BTRFS I would likely use subvolumes. Only
thing I may separate would be /home to make it easier on a re-installation of
the OS to keep it around. That said, I never ever reinstalled the Debian on
this ThinkPad T520 since I initially installed it. And on previous laptops I
even copied the Debian on the older laptop onto the newer laptop. With the
T520 I reinstalled, cause I wanted to switch to 64 bit cleanly.
Yeah, small partitions make sense in some cases, but in a lot of places
they're typically used, there are perfectly legitimate reasons to
suddenly need multiple gigabytes of extra space for a short period of
time. In my case, the only partition that I have split out that's less
than a few GB is /boot, but I usually split out /usr/src and
/usr/portage, because I need them to be fast, and run /tmp and /var/tmp
on tmpfs (so technically split out). I personally see little value in
splitting out /home on a single user system unless you're multi-booting
or planning to switch distros at some point (or are running a distro
that needs special handling to do release upgrades).
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