Lustre discuss - Jul 2009 - detecting problematic files via mds/oss syslog messages

Hi there,

Are there any ways of detecting the problematic file names from the mds/oss
syslog messages? Or to be more definite, are there any ways to find a map of
file name to inode number or file name to object id or inode number to
object id? I''m trying to understand the insights of lustre and some
times I
wonder which files are affected from a lustre error? For example, when I see
an object id in log messages, how can I understand which file is this? Is
there any look up table, or map for these purposes?

Thanks in advance.

Regards,

Ender GULER
System Administrator
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On Jul 20, 2009  13:20 +0300, Ender G?ler wrote:
> Are there any ways of detecting the problematic file names from the mds/oss
> syslog messages? Or to be more definite, are there any ways to find a map
of
> file name to inode number or file name to object id or inode number to
> object id? I''m trying to understand the insights of lustre and
some times I
> wonder which files are affected from a lustre error? For example, when I
see
> an object id in log messages, how can I understand which file is this? Is
> there any look up table, or map for these purposes?
If there are particularly bad error messages, you could file a bug with
details.

It is also possible to manually map an OST object ID to an MDS filename.
For example, objid 620032 on my filesystem:

ost# debugfs -c -R "stat /O/0/d$((620032 %32))/620032"
/dev/vgmyth/lvmythost0
Inode: 31905   Type: regular    Mode:  0666   Flags: 0x80000
User:  1000   Group:  1000   Size: 461317
:
:
Extended attributes stored in inode body: 
  fid = "f8 3f 26 00 00 00 00 00 f1 0a 44 41 00 00 00 00 00 76 09 00 00 00
00 00 00 00 00 00 00 00 00 00 " (32)

The important part is the "Extended attributes", which map to

struct filter_fid {
        struct ll_fid {
                __u64 id;         /* holds object id */
                __u32 generation; /* holds object generation */
                __u32 f_type;     /* file stripe number */
        };
	__u64           ff_objid;
	__u64           ff_group;
};

So, this object maps to inode 0x00263ff8 on the MDS.  There:

mds# debugfs -c -R "ncheck 0x00263ff8" /dev/vgmyth/lvmythmds0
2506744 /ROOT/backup/Picture Archives/2003 Archives/2003-09-28/P1010034.JPG


It is of course possible to start directly from an inode number on the MDS,
or an inode number on the OST.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

On Mon, 2009-07-20 at 16:06 -0600, Andreas Dilger wrote:
> On Jul 20, 2009  13:20 +0300, Ender G?ler wrote:
> > Are there any ways of detecting the problematic file names from the
mds/oss
> > syslog messages? Or to be more definite, are there any ways to find a
map of
> > file name to inode number or file name to object id or inode number to
> > object id? I''m trying to understand the insights of lustre
and some times I
> > wonder which files are affected from a lustre error? For example, when
I see
> > an object id in log messages, how can I understand which file is this?
Is
> > there any look up table, or map for these purposes?
> 
> If there are particularly bad error messages, you could file a bug with
> details.
> 
> It is also possible to manually map an OST object ID to an MDS filename.
> For example, objid 620032 on my filesystem:
This exact procedure is being added to the manual FWIW.  Details are in
bug 19753.

b.

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Andreas and Brian,

Thank you for invaluable information you gave.

Regards,

Ender GULER

On Tue, Jul 21, 2009 at 4:51 PM, Brian J. Murrell <Brian.Murrell at
sun.com>wrote:
> On Mon, 2009-07-20 at 16:06 -0600, Andreas Dilger wrote:
> > On Jul 20, 2009  13:20 +0300, Ender G?ler wrote:
> > > Are there any ways of detecting the problematic file names from
the
> mds/oss
> > > syslog messages? Or to be more definite, are there any ways to
find a
> map of
> > > file name to inode number or file name to object id or inode
number to
> > > object id? I''m trying to understand the insights of
lustre and some
> times I
> > > wonder which files are affected from a lustre error? For example,
when
> I see
> > > an object id in log messages, how can I understand which file is
this?
> Is
> > > there any look up table, or map for these purposes?
> >
> > If there are particularly bad error messages, you could file a bug
with
> > details.
> >
> > It is also possible to manually map an OST object ID to an MDS
filename.
> > For example, objid 620032 on my filesystem:
>
> This exact procedure is being added to the manual FWIW.  Details are in
> bug 19753.
>
> b.
>
>
> _______________________________________________
> Lustre-discuss mailing list
> Lustre-discuss at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-discuss
>
>
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