I will restate the problem I am having with Lustre.
With my I/O instrumentation library, I want to use
*llapi_file_get_stripe*() to find the OSTs that a file of interest is
striped on and then monitor only those OST's using files in the
directory /proc/fs/lustre/osc. This needs to be done programmatically,
and in a general sense, with potentially only a relative path name.
*llapi_file_get stripe*() yields
lmm_stripe_count: 1
lmm_stripe_size: 1048576
lmm_pattern: 1
lmm_layout_gen: 0
lmm_stripe_offset: 12
lmm_oi.oi_fid *0x**194aa*
*obdidx* objid objid group
*12* 31515860 0x1e0e4d4 0
If I use *obdidx=12=0xc *to find the OST in directory
/proc/fs/lustre/osc, I get multiple OSTs as there are multiple file
systems with an ost of index 12 ( note that obdidx is decimal and
entries in */proc/fs/lustre/osc* are hexadecimal, so we are looking for
OST000c ).
%ls -ld /proc/fs/lustre/osc/*OST000c*
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp1-OST000c-osc-ffff88090509f000
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp2-OST000c-osc-ffff881038061c00
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp6-OST000c-osc-ffff88084c405400
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp7-OST000c-osc-ffff8807a8e1d400
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp8-OST000c-osc-ffff88078339b800
dr-xr-xr-x 2 root root 0 Jul 18 14:31
/proc/fs/lustre/osc/nbp9-OST000c-osc-ffff8807833a5400
So I need to figure out which directory entry applies to the OST of my
file of interest.
I looked at the inode for clues. I did an stat() of the file to get
dev_t st_dev=0xcc5d43c2
ino_t st_ino=0x2000311ed0194aa
I notice the *lov_user_md->oi_fid=0x0194aa,* populated by
*llapi_file_get_stripe*(), is reflected in the lower part of
*stat.st_ino=0x2000311ed0194aa*. My question is, "Does the remainder of
st_ino, *2000311ed*, give me any clue as to which OST I should use out
of */proc/fs/lustre/osc*?" The same question applies to the OST's
objid=0x1e0e4d4and the file's st_dev=0xcc5d43c2.
Because I know a priori that the file is in the lov nbp2, I know I need
to find /proc/fs/lustre/osc/*nbp2-OST000c-osc-ffff881038061c00.***What
does the
*ffff881038061c00 *represent? It is the same value for all OST's in a
given lov, so I am guessing it is lov related.*
*
There are over 1200 OST on the node, so I want to minimize the number
that I instrument.
Any information that would shed some light on this would be greatly
appreciated.
John
--
I/O Doctors, LLC
507-766-0378
[email protected]
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