LVM Striping vs Default LVM performance ?

Harishkumar .Pathangay

LVM Striping vs Default LVM performance ?

Hi,

I used LOAD utility to load data into a tablespace with 1 container on LVM with 2 physical disks, DB2_PARALLEL_IO is also set to 2. it took about 22 mins.

repeated the same test case with tablespace with 1 container on LVM with 1 physical disk. it takes the same 22 mins.

Parallel writing is happening for sure when I observe iostat output on physical devices [/dev/sdb1,sdd1].but getting same speed of writing around 900kbps. Each physical device is capable of 1Mbps. So was expecting parallel writing of containers should improve write times. but seems not.

Any thoughts?

Please be aware of all these things are happening in a VM.

thanks,

harish pathangay

Mark Barinstein

RE: LVM Striping vs Default LVM performance ?
(in response to Harishkumar .Pathangay)

Hi,

DB2_PARALLEL_IO and LOAD are unrelated. Try the LOAD DISK_PARALLELISM option.

Harishkumar .Pathangay

RE: LVM Striping vs Default LVM performance ?
(in response to Mark Barinstein)

hi,

I tried that too. I have both set, the registry variable and disk_parallelism of load command.

I also observed that I am not able to see id diaglog what is the parallelism used by load command.

thanks for quick response. I am sorry should have mentioned it earlier. db2 11.1.3.3 on ubuntu Linux in a vm.

thanks, harish p

Harishkumar .Pathangay

RE: LVM Striping vs Default LVM performance ?
(in response to Harishkumar .Pathangay)

Hi,

If I have one disk controller with 3 disks attached to it, each disk with 1Mbps io rate , will it divide the IO rate by 3? meaning the striped lvm provides only 300kbps io rate.

I repeated the test case with 2 disks, it is giving me 450kbs, half of 900kbps.

my observations are pointing to that only. but as usual confirmation is helpful.

thanks, harish pathangay

Harishkumar .Pathangay

RE: LVM Striping vs Default LVM performance ?
(in response to Harishkumar .Pathangay)

Hi,

I even tried with 2 containers in a tablespace with load utility parallelism 2.

it splits the io rate. I am getting io parallel, but my io rate is divided by two. just wondering why it is that way?

I am using VM with Virtual Hard Disks of SATA type with single SATA Controller.

thanks,

harish pathangay