topic slow performance on logical volumes in Operating System - Linux

slow performance on logical volumes

msmalik0101 — Wed, 10 Apr 2013 15:10:51 GMT

its a SUSE 11 SP2 xen virtual machine with 8 GB Memory, kernel version 3.0.58-0.6.6-xen #1 SMP

we recently changed the traditional/static partitioning(/dev/xvdc{1,2,3} to lvm based volumes, and after that we are observing serious performance issues. e.g earlier(when we were using static/traditional partitioning) backup took only 45 minutes, now backup takes 2 hours or more. Also our end users are complaining about performance too.

following are storage details:
df -hT
Filesystem                                      Type      Size Used Avail Use% Mounted on
/dev/xvda3                                      ext3       47G 7.6G   38G 17% /
devtmpfs                                        devtmpfs 4.1G 140K 4.1G   1% /dev
tmpfs                                           tmpfs     8.0G 179M 7.9G   3% /dev/shm
/dev/xvda1                                      ext3      243M   24M 207M 11% /boot
/dev/mapper/VG--ORG--ORACLE-sap--oracle         ext3      245G 222G   11G 96% /oracle
/dev/mapper/VG--ORG--ORACLE-sap--ora--sapmnt    ext3       15G 1.7G   13G 12% /sapmnt
/dev/mapper/VG--ORG--ORACLE-sap--ora--usrsap    ext3       30G   24G 4.3G 85% /usr/sap

# pvscan
PV /dev/xvdc    VG VG-ORG-ORACLE   lvm2 [350.00 GiB / 7.00 GiB free]

# vgscan
Reading all physical volumes. This may take a while...
Found volume group "VG-ORG-ORACLE" using metadata type lvm2

# /sbin/lvs
sap-ora-sapmnt    VG-ORG-ORACLE -wi-ao 15.00g
sap-ora-usrsap    VG-ORG-ORACLE -wi-ao 30.00g
sap-oracle        VG-ORG-ORACLE -wi-ao 248.00g

running "hdparm -t" on the raw disk /dev/xvdc returns far better results then running "hdparm -t" on logical volumes

/dev/xvdc:
Timing buffered disk reads: 742 MB in 3.00 seconds = 247.31 MB/sec

/dev/xvdc:
Timing buffered disk reads: 670 MB in 3.00 seconds = 223.31 MB/sec

/dev/xvdc:
Timing buffered disk reads: 718 MB in 3.00 seconds = 239.23 MB/sec
[/code]

while running "hdparm -t" on logical volume returns very slow results:

/dev/mapper/VG--ORG--ORACLE-sap--oracle:
Timing buffered disk reads: 148 MB in 3.01 seconds = 49.17 MB/sec

/dev/mapper/VG--ORG--ORACLE-sap--oracle:
Timing buffered disk reads: 192 MB in 3.10 seconds = 62.02 MB/sec

/dev/mapper/VG--ORG--ORACLE-sap--oracle:
Timing buffered disk reads: 154 MB in 3.03 seconds = 50.87 MB/sec

/dev/mapper/VG--ORG--ORACLE-sap--oracle:
Timing buffered disk reads: 184 MB in 3.03 seconds = 60.77 MB/sec

Please help and suggest

Re: slow performance on logical volumes

msmalik0101 — Wed, 10 Apr 2013 15:16:59 GMT

also for your kind information

pvdisplay
--- Physical volume ---
PV Name               /dev/xvdc
VG Name               VG-ORG-ORACLE
PV Size               350.00 GiB / not usable 4.00 MiB
Allocatable           yes
PE Size               4.00 MiB
Total PE              89599
Free PE               1791
Allocated PE          87808
PV UUID               jhypNN-fPpy-2uzc-nsxP-qZIl-9JAg-O9aenE

vgdisplay
--- Volume group ---
VG Name               VG-ORG-ORACLE
System ID
Format                lvm2
Metadata Areas        1
Metadata Sequence No 6
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                4
Open LV               4
Max PV                0
Cur PV                1
Act PV                1
VG Size               350.00 GiB
PE Size               4.00 MiB
Total PE              89599
Alloc PE / Size       87808 / 343.00 GiB
Free PE / Size       1791 / 7.00 GiB
VG UUID               MSnb2T-A5Pf-3i7B-5sz2-f10M-2T2s-uCbdJn

lvdisplay
--- Logical volume ---
LV Name                /dev/VG-ORG-ORACLE/sap-ora-sapmnt
VG Name                VG-ORG-ORACLE
LV UUID                mSM4Mg-jxoV-phr5-8p5S-i5XY-VSbN-p6McFk
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                15.00 GiB
Current LE             3840
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     1024
Block device           253:0

--- Logical volume ---
LV Name                /dev/VG-ORG-ORACLE/sap-ora-usrsap
VG Name                VG-ORG-ORACLE
LV UUID                zbwf4e-E3HL-6Vnw-ayXK-19PH-Dtir-uqi52g
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                30.00 GiB
Current LE             7680
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     1024
Block device           253:1

--- Logical volume ---
LV Name                /dev/VG-ORG-ORACLE/sap-oracle
VG Name                VG-ORG-ORACLE
LV UUID                4zt2BF-BhIJ-a4I7-mr9i-KVBk-c6Dt-BvztDQ
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                248.00 GiB
Current LE             63488
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     8192
Block device           253:2

--- Logical volume ---
LV Name                /dev/VG-ORG-ORACLE/oracle-sap-backup
VG Name                VG-ORG-ORACLE
LV UUID                vXL33N-CaUY-ILsT-YwqE-Hn0Z-xLRV-Pm2aRS
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                50.00 GiB
Current LE             12800
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     1024
Block device           253:3

Re: slow performance on logical volumes

msmalik0101 — Wed, 10 Apr 2013 19:58:16 GMT

I think I have found the solution.

our XEN hypervisor(dom0) is using LVM, and we are also using lvm on our virtual machines(domU).. which is not recommend

as per https://www.suse.com/support/kb/doc.php?id=3559698

Only use Logical Volume Manager (LVM) on Dom0 or DomU, but not both

Regards