[gpfsug-discuss] What NSDs does a file have blocks on?

[Kumaran Rajaram]

Hi Kevin,

>>I want to know what NSDs a single file has its’ blocks on?

You may use /usr/lpp/mmfs/samples/fpo/mmgetlocationto obtain the 
file-to-NSD block layout map. Use the -h option for this tools usage (
mmgetlocation -h). 

Sample output is below:

# File-system block size is 4MiB and sample file is 40MiB.
# ls -lh /mnt/gpfs3a/data_out/lf
-rw-r--r-- 1 root root 40M Jul  9 16:42 /mnt/gpfs3a/data_out/lf
# du -sh /mnt/gpfs3a/data_out/lf
40M     /mnt/gpfs3a/data_out/lf
# mmlsfs gpfs3a | grep 'Block size'
 -B                 4194304                  Block size

# The file data is striped across 10 x NSDs (DMD_NSDX) constituting the 
file-system

# /usr/lpp/mmfs/samples/fpo/mmgetlocation -f /mnt/gpfs3a/data_out/lf
[FILE /mnt/gpfs3a/data_out/lf INFORMATION]
         FS_DATA_BLOCKSIZE : 4194304 (bytes)
         FS_META_DATA_BLOCKSIZE : 4194304 (bytes)
         FS_FILE_DATAREPLICA : 1
         FS_FILE_METADATAREPLICA : 1
         FS_FILE_STORAGEPOOLNAME : system
         FS_FILE_ALLOWWRITEAFFINITY : no
         FS_FILE_WRITEAFFINITYDEPTH : 0
         FS_FILE_BLOCKGROUPFACTOR : 1

chunk(s)# 0 (offset 0) : [DMD_NSD5 c72f1m5u37ib0,c72f1m5u39ib0]
chunk(s)# 1 (offset 4194304) : [DMD_NSD6 c72f1m5u39ib0,c72f1m5u37ib0]
chunk(s)# 2 (offset 8388608) : [DMD_NSD7 c72f1m5u37ib0,c72f1m5u39ib0]
chunk(s)# 3 (offset 12582912) : [DMD_NSD8 c72f1m5u39ib0,c72f1m5u37ib0]
chunk(s)# 4 (offset 16777216) : [DMD_NSD9 c72f1m5u37ib0,c72f1m5u39ib0]
chunk(s)# 5 (offset 20971520) : [DMD_NSD10 c72f1m5u39ib0,c72f1m5u37ib0]
chunk(s)# 6 (offset 25165824) : [DMD_NSD1 c72f1m5u37ib0,c72f1m5u39ib0]
chunk(s)# 7 (offset 29360128) : [DMD_NSD2 c72f1m5u39ib0,c72f1m5u37ib0]
chunk(s)# 8 (offset 33554432) : [DMD_NSD3 c72f1m5u37ib0,c72f1m5u39ib0]
chunk(s)# 9 (offset 37748736) : [DMD_NSD4 c72f1m5u39ib0,c72f1m5u37ib0]


[FILE: /mnt/gpfs3a/data_out/lf SUMMARY INFO]
replica1:
        c72f1m5u37ib0,c72f1m5u39ib0: 5 chunk(s)
        c72f1m5u39ib0,c72f1m5u37ib0: 5 chunk(s)

Thanks and Regards,
-Kums






From:   "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   07/09/2018 04:05 PM
Subject:        [gpfsug-discuss] What NSDs does a file have blocks on?
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



Hi All, 

I am still working on my issue of the occasional high I/O wait times and 
that has raised another question … I know that I can run mmfileid to see 
what files have a block on a given NSD, but is there a way to do the 
opposite?  I.e. I want to know what NSDs a single file has its’ blocks on? 
 The mmlsattr command does not appear to show this information unless it’s 
got an undocumented option.  Thanks…

Kevin

—
Kevin Buterbaugh - Senior System Administrator
Vanderbilt University - Advanced Computing Center for Research and 
Education
Kevin.Buterbaugh at vanderbilt.edu - (615)875-9633


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