Re: general thoughts and questions + general and RAID5/6 stability?

["Stefan G. Weichinger" <lists@xunil.at>]

Am 23.09.2014 um 15:38 schrieb Austin S Hemmelgarn:

>> What features for example?
> Well, running 'mkfs.btrfs -O list-all' with 3.16 btrfs-progs gives the
> following list of features:
> mixed-bg        - mixed data and metadata block groups
> extref            - increased hard-link limit per file to 65536
> raid56            - raid56 extended format
> skinny-metadata        - reduced size metadata extent refs
> no-holes        - no explicit hole extents for files
> 
> mixed-bg is something that you generally wouldn't want to change after
> mkfs.
> extref can be enabled online, and the filesystem metadata gets updated
> as-needed, and dosen't provide any real performance improvement (but is
> needed for some mail servers that have HUGE mail-queues)
> I don't know anything about the raid56 option, but there isn't any way
> to change it after mkfs.
> skinyy-metadata can be changed online, and the format gets updated on
> rewrite of each metadata block.  This one does provide a performance
> improvement (stat() in particular runs noticeably faster).  You should
> probably enable this if it isn't already enabled, even if you don't
> recreate your filesystem.
> no-holes cannot currently be changed online, and is a very recent
> addition (post v3.14 btrfs-progs I believe) that provides improved
> performance for sparse files (which is particularly useful if you are
> doing things with fixed size virtual machine disk images).

Recreating or at least "btrfstune -rx" for my rootfs would mean that I
have to boot from a live medium bringing recent btrfs-progs, right?

sysresccd brings btrfs-progs-3.14.2 ... that should be enough, ok?

aside from that, the rootfs on my thinkpad shows these features:

# ls /sys/fs/btrfs/bec7dff9-8749-4db4-9a1b-fa844cfcc36a/features/
big_metadata  compress_lzo  extended_iref  mixed_backref

So I only miss the skinny extents ... and "no-holes".

Stefan