Thanks Steve; That solves that question. Now for the next one which was my
real intent (I was just using the wrong terminology).
Setup:
xfs partition that is 3G in size using 4K block size
external log on a different partition that is 1G in size, again using 4K
blocks.
When I created this partition with the external log, I used the maximum log
size that mkfs.xfs would allow (-l logdev=/dev/hdc1,size=32768b)
As I said in my earlier message, I make extensive use of extended attributes
and I need to monitor how much metadata I have stored on disk.
I have gone through the man page and online help of xfs_db, and I have to
admin some of information is above my knowledge level, but I have not been
able to discover anything for what I am looking for.
Basically: how much metadata (in bytes, kb, or mb) do I have sitting on the
disk.
Is there such a command or sequence of commands?
Thanks;
Joe
On Friday 04 October 2002 11:49 am, Steve Lord wrote:
> On Fri, 2002-10-04 at 07:56, Joe Bacom wrote:
> > Hi Folks;
> >
> > Hopefully this is an easy question. I would like to know how to
> > determine the amount of usage / free space that is left in the journal.
> > I have several filesytems that make heavy use of extended attributes, so
> > I would like to monitor the journal space to ensure that I don't try to
> > overfill it.
>
> Sending this out since folks are getting confused....
>
> The xfs journal (or log, it is called log in the code), is basically
> a circular on disk buffer. Metadata changes are recorded into the log,
> and subsequently the real metadata is flushed to disk. The benefits of
> having a log is we write all the changes which make the filesystem
> move from one consistent state to another out into the log in one
> go rather than having to sync up several writes to different parts
> of the disk. Those writes out to the real metadata happen later, but
> we do not care at all about the order they happen in.
>
> So we perform some transactions, these are written to the log, and
> our location in the log keeps moving, eventually wrapping around.
> Normally before we wrap the metadata modified in a transaction has
> been flushed to disk, so we can just reuse the space. If we are
> modifying the filesystem faster than metadata can be flushed to
> disk then new operations which need log space have to force the
> old metadata out to disk first.
>
> So you cannot 'run out' of log space, but you can get into the
> mode we call tail pushing where the head of the log is always
> bumping into the tail.
>
> Steve
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