On 17.06.2014 22:37, Dave Chinner wrote:
> On Tue, Jun 17, 2014 at 10:26:51AM +0200, Matthias Schniedermeyer wrote:
> > Hi
> > How seriously meant is "V5 isn't experimental anymore"?
> "Fully supported" isn't a clear enough statement?
I guess that was a "selective memory"-bug on my side.
> > I ask because the man-page only mentions the syntax to enable it by
> > accident. A.k.a. the backport of ftype to V4.
> > (man-page of xfsprogs 3.2.0 in Debian-SID)
> That's intentional. V5 superblocks are an implementation detail that
> most users don't even need to know about. They care about the name
> of the features they are enabling at mkfs time, not the details of
> the on-disk implementation of those features.
The question still stands.
The crc-option is only mentioned "by accident".
Without the ftype backport there would be no mention of the "feature
Furthermore i suspect that the ftype-feature also wouldn't be mentionted
without the V4 backport.
Which beggs the question, what other features are "burried" in V5 that
aren't mentioned in the man-page.
And are there any other "-m" options, because "-m" (asside from the
ftype accident) is completly undocumented.
> > And you still have to know that crc means V5.
> Why do you care about the format mkfs.xfs chooses for you - it's
> based on the features you requested. V5 isn't magically faster than
I find the crc feature relativly important.
I personally had exprienced an USB enclosure(-model. As in i had several
of those) that under rare circumstances flipped or cleared a single bit
in a specific bit-pattern). Such corruption most likely ends up inside a
data-file because most times there is more data than meta-data. But
COULD happend inside the meta-data.
Since that day i have nearly everything MD5(or SHA256)ed so i can at
least detect if i have a data-corruption.
Fortunatly that never happend again after i replaced that enclosure
model. Which i can say with pretty high confidence.
> V4 - there are many cases where it is slower due to CRC overhead
> or the overhead of the larger inode it requires. So unless you
> request a feature that requires it at mkfs time, you don't get that
Are there any feature besides crc/ftype in V5?
But i guess for "-n type=1" i would get a V4 + feature_bit.
And "-m crc=1" chooses V5 and i get ftype as a bonus (If i understand
> In a year or so we'll change the mkfs default so that CRCs are
> enabled by default, but we can't do that until all the distro's have
> had time to pick up a kernel that fully supports the CRC feature....
OK. So V5 will be the future default.