Re: [gentoo-user] btrfs strategies (wasHard drive noise)

[J. Roeleveld]

On Sunday, December 20, 2015 02:15:33 AM covici@××××××××××.com wrote:
> covici@××××××××××.com wrote:
> > Rich Freeman <rich0@g.o> wrote:
> > > On Sat, Dec 19, 2015 at 2:56 AM,  <covici@××××××××××.com> wrote:
> > > > I was never able to get either zfs or btrfs to work correctly, zfs was
> > > > very vulnerable -- I forgot to export a zfs on a usb drive and got an
> > > > enless loop of processes untill I rebooted.  Btrfs never did work for
> > > > me, I created a pool,  copied my root file system, usr and var into
> > > > ssubvolumes, and copied my files, but when I would boot into it,
> > > > everything was messed up, processes thought files were missing, very
> > > > strange.  So, how did you set up either one of those -- I would love
> > > > to
> > > > use it because I have ssds and I don't want to rely on their firmware
> > > > either.
> > >
> > > Well, I don't have much personal experience with zfs, but the ZFS on
> > > Linux lead is a Gentoo dev, so you're in good company there all the
> > > same.  I personally use btrfs.
> > >
> > > The obvious caveat is that it is still relatively experimental, and
> > > raid5/6 is VERY experimental.  I plan to convert to raid5/6 at a
> > > future date but am staying away from it for now (and a selling point
> > > of btrfs is that reshaping in-place is easy).
> > >
> > > I can't really vouch for what went wrong with your migration.  It
> > > could be anything from a failure to preserve all your file attributes
> > > to something with btrfs itself or your bootloader config/etc.  It
> > > isn't hard to do a new install in btrfs though, and you can always
> > > mess with it in a VM, or even mess with doing migrations in a VM.
> > >
> > > My btrfs install notes are at:
> > > https://docs.google.com/document/d/1VJlJyYLTZScta9a81xgKOIBjYsG3_VfxxmUS
> > > xG23Uxg/edit?usp=sharing (I still plan to merge this stuff into the
> > > handbook.  Maybe a good holiday project...  Oh, and if it isn't already
> > > obvious anybody can add comments and half this list seems to have
> > > already done so.)
> > >
> > > Oh, for a boot image I tend to use system rescue CD since it has all
> > > the necessary userspace and is gentoo-based (and you can always emerge
> > > --sync and install whatever you need inside it).  I tend to use the
> > > alternate kernel since it is newer, and with btrfs newer tends to be
> > > better.  In production I'm currently on 3.18 eyeing an upgrade to 4.1.
> > > I tend to stay on the latest longterm, but not when they are first
> > > declared as longterm.  That seems to be the sweet spot for getting
> > > btrfs features and bugfixes, but not getting as many of the
> > > regressions.  I use grub2/dracut to boot, and that is in my guide.
> > >
> > > If you follow those notes for a stage3 install it should "just work."
> > > If you want to mess around I suggest just doing a vanilla install on a
> > > VM once to validate that it works for you and then tweak from a
> > > position of strength.
> >
> > Thanks.  I will check out your notes and figure out something -- it was
> > definitely strange.  I have a vm I can play with -- its older, but I can
> > bring it up to date and see what happens.
> >
> > Thanks again.
>
> One thing I was thinking of -- since I like separate file systems for
> each major directory i.e. separate /usr, /var, /home, /tmp and even
> /var/tmp/portage, I thought I would make btrfs file systems using lvm.
> The advantage is that I use lvm already, so this would be easy for me to
> do and safer in case one of them goes south and easier to control  space
> allocation.  The only disadvantage I can see is if its a performance
> hit, does anyone have any knowledge of that is true?

I only played around with ZFS so far, but I believe the same holds true for 
BTRFS.

These new filesystems should really be handed control of the entire disk as 
they already include LVM-like functionality.
You can create subvolumes and limit those to different sizes if you so desire.

When using an additional layer between ZFS/BTRFS and the discs, you will loose 
performance with no gain in flexibility.

--
Joost