Re: Why could different data in a table be processed with different performance?

> 1) Which file system are you using?
From Linux's view it's ext4. Real vmdx file on Hyper-V is stored on NTFS,
as far as I know.

> 2) What is the segment layout of the LVM PVs and LVs?
I am a bit lost with it. Is that what you are asking about?
master:
# pvs --segments
PV VG Fmt Attr PSize PFree Start SSize
/dev/sda5 ubuntu-vg lvm2 a-- 19.76g 20.00m 0 4926
/dev/sda5 ubuntu-vg lvm2 a-- 19.76g 20.00m 4926 127
/dev/sda5 ubuntu-vg lvm2 a-- 19.76g 20.00m 5053 5
# lvs --segments
LV VG Attr #Str Type SSize
root ubuntu-vg -wi-ao--- 1 linear 19.24g
swap_1 ubuntu-vg -wi-ao--- 1 linear 508.00m

slave:
# pvs --segments
PV VG Fmt Attr PSize PFree Start SSize
/dev/sda3 postgresnlpslave-vg lvm2 a-- 429.77g 0 0 110021
/dev/sda5 postgresnlpslave-vg lvm2 a-- 169.52g 0 0 28392
/dev/sda5 postgresnlpslave-vg lvm2 a-- 169.52g 0 28392 2199
/dev/sda5 postgresnlpslave-vg lvm2 a-- 169.52g 0 30591 2560
/dev/sda5 postgresnlpslave-vg lvm2 a-- 169.52g 0 33151 10246
/dev/sdb1 postgresnlpslave-vg lvm2 a-- 512.00g 0 0 131071
# lvs --segments
LV VG Attr #Str Type SSize
root postgresnlpslave-vg -wi-ao---- 1 linear 110.91g
root postgresnlpslave-vg -wi-ao---- 1 linear 40.02g
root postgresnlpslave-vg -wi-ao---- 1 linear 10.00g
root postgresnlpslave-vg -wi-ao---- 1 linear 429.77g
root postgresnlpslave-vg -wi-ao---- 1 linear 512.00g
swap_1 postgresnlpslave-vg -wi-ao---- 1 linear 8.59g

> 3) Do you use LVM for any "extra" features, such as snapshots?
I don't think so, but how to check? vgs gives #SN = 0, is that it?

> 4) You can try using seekwatcher to see where on the disk the slowness is
occurring. You get a chart similar to this
http://kernel.dk/dd-md0-xfs-pdflush.png
> 5) BCC is a collection of tools that might shed a light on what is
happening. https://github.com/iovisor/bcc
Will look into it.

Regards,
Vlad