[Ocfs2-users] Understanding debugfs.ocfs2 output

[Norman P. B. Joseph]

Sunil,

Thanks, that answers question #1 and maybe also question #2.  Would it
be safe to assume then, that only when -all- of the Contig numbers in
the extent_alloc output fall below the Clusters per Group X Bits per
Cluster number is the "no space" issue triggered?

-Norm


On Tue, 2010-11-23 at 14:39 -0800, Sunil Mushran wrote:
> The length of allocator chains in the global bitmap depends on
> the size of the volume and block/cluster sizes. It is created during
> format and only grows if the volume is grown. That's it.
> 
> On 11/23/2010 11:04 AM, Norman P. B. Joseph wrote:
> > This is related to the "No space on OCFS2 volume" error discussed here
> > this past Sep/Oct.  Our Oracle support rep pointed us to Metalink note
> > #1232702.1 and suggested we should script something up to periodically
> > check the free contiguous blocks in the group chains for the volume in
> > question.
> >
> > Reading the note, I get how to get Clusters per Group X Bits per Cluster
> > from the "stat //extent_alloc:NNNN".  What I'm confused about is parsing
> > the "stat //global_bitmap" section, and I thought I might have a better
> > chance of getting an explanation from the audience here.
> >
> > I have 2 basic questions:
> >
> > 1) The note above says that a "highly fragmented volume will have many"
> > Group Chain entries in the //global_bitmap section, but gives no
> > guidance as to what constitutes "many".  I see ~240 in the 56 GB OCFS2
> > partition in question.  Is that Low?  High?  Just Right?
> >
> > 2) The note also says to check the "Contig" values in the long list of
> > Group Chains that follows in the //global_bitmap section.  Specifically,
> > "If none are higher than the sum[sic] of "Clusters per Group * Bits per
> > Cluster" the metadata extent file cannot be expanded..."  Here is a
> > sample output below:
> >
> >          Group Chain: 8   Parent Inode: 11  Generation: 1861766630
> >          CRC32: 00000000   ECC: 0000
> >          ##   Block#            Total    Used     Free     Contig   Size
> >          0    258048            32256    1026     31230    28159    4032
> >          1    8096256           32256    1        32255    32255    4032
> >
> >          Group Chain: 9   Parent Inode: 11  Generation: 1861766630
> >          CRC32: 00000000   ECC: 0000
> >          ##   Block#            Total    Used     Free     Contig   Size
> >          0    290304            32256    30721    1535     1535     4032
> >          1    8128512           32256    1        32255    32255    4032
> >
> >          Group Chain: 10   Parent Inode: 11  Generation: 1861766630
> >          CRC32: 00000000   ECC: 0000
> >          ##   Block#            Total    Used     Free     Contig   Size
> >          0    322560            32256    31745    511      511      4032
> >          1    8160768           32256    1        32255    32255    4032
> >
> >          Group Chain: 11   Parent Inode: 11  Generation: 1861766630
> >          CRC32: 00000000   ECC: 0000
> >          ##   Block#            Total    Used     Free     Contig   Size
> >          0    354816            32256    30721    1535     1535     4032
> >          1    8193024           32256    1        32255    32255    4032
> >
> > Should I be considering -all- the Contig values from -all- the Group
> > Chains listed when looking for issues, or should I be considering each
> > chain individually?  IOW, is it only a problem when -all- the Contig
> > values from -all- the chains are below the clusters X bits value, or is
> > it only a problem when all of the Contig values for a -single- chain are
> > below the cluster X bits value?
> >
> > Any pointers on valid interpretation of the output is appreciated.
> >
> > -Norm
> >
> >
-- 
Norman Joseph, Senior System Engineer              joseph at ctc.com
Concurrent Technologies Corporation                 814.269.2633
Information Systems Management Office (ISMO)



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