[LU-19106] Metadata Performance Degradation in OST Pool

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.17.0
• Environment: server=2.16.56_39_g99f47b1 ; client=2.16.56_39_g99f47b1
• Severity: 3
• Assignee: Emoly Liu
• Reporter: Shuichi Ihara

Description

FIle Creation rate is low when OST pool is configured.
This happens even if OSTs are empty. The OSTs allocation should be RR mode in both cases and shouldn't be QoS mode.

[root@src01-c0-n0 ~]# lfs df
UUID                   1K-blocks        Used   Available Use% Mounted on
testfs-MDT0000_UUID    560019536       18140   553357684   1% /testfs[MDT:0] 
testfs-MDT0001_UUID    560019536       18072   553357752   1% /testfs[MDT:1] 
testfs-MDT0002_UUID    560019536       18084   553357740   1% /testfs[MDT:2] 
testfs-MDT0003_UUID    560019536       18092   553357732   1% /testfs[MDT:3] 
testfs-OST0000_UUID   6365630144        1804  6301187448   1% /testfs[OST:0] 
testfs-OST0001_UUID   6365630144        1804  6301187448   1% /testfs[OST:1] 
testfs-OST0002_UUID   6365630144        1808  6301187444   1% /testfs[OST:2] 
testfs-OST0003_UUID   6365630144        1812  6301187440   1% /testfs[OST:3] 
testfs-OST0004_UUID   6365630144        1812  6301187440   1% /testfs[OST:4] 
testfs-OST0005_UUID   6365630144        1816  6301187436   1% /testfs[OST:5] 
testfs-OST0006_UUID   6365630144        1820  6301187432   1% /testfs[OST:6] 
testfs-OST0007_UUID   6365630144        1820  6301187432   1% /testfs[OST:7] 


filesystem_summary:  50925041152       14496 50409499520   1% /testfs 

Here is a reproducer and test results

lctl pool_new testfs.8ost
lctl pool_add testfs.8ost OST[0-7]

mkdir /testfs/nopool /testfs/pool
lfs setstripe -p 8ost /testfs/pool

mpirun -np 512 mdtest -F -u -n 2000 -N 1 -i 3 -p 10 -d /testfs/nopool/ -v
mpirun -np 512 mdtest -F -u -n 2000 -N 1 -i 3 -p 10 -d /testfs/pool/ -v

/wo pool

SUMMARY rate: (of 3 iterations)
   Operation                      Max            Min           Mean        Std Dev
   ---------                      ---            ---           ----        -------
   File creation             :     426796.113     383108.976     403677.931      17923.375
   File stat                 :    1554256.632     896794.266    1316016.009     297345.579
   File read                 :     850121.885     804149.111     832731.467      20361.493
   File removal              :     253626.293     251165.781     251989.428       1155.988
   Tree creation             :         23.846          1.905          9.407         10.212
   Tree removal              :         29.018         22.761         26.421          2.663

w/ OST pool

SUMMARY rate: (of 3 iterations)
   Operation                      Max            Min           Mean        Std Dev
   ---------                      ---            ---           ----        -------
   File creation             :     260143.504     253626.126     257061.515       2671.407
   File stat                 :    1568786.269     923061.589    1341791.005     296426.560
   File read                 :     838229.567     706947.471     757857.605      57486.753
   File removal              :     273156.410     257635.982     264259.176       6535.374
   Tree creation             :         22.053          2.150          8.959          9.262
   Tree removal              :         29.228         19.743         25.030          3.948