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Slow reading speed of ploops [message #52931] Sun, 27 August 2017 23:55 Go to next message
Juves is currently offline  Juves
Messages: 4
Registered: August 2017
Junior Member
In the ploop the reading speed dramatically slow down.
In 2-4 times, depended with vhd space.
Containers don't have IO limitations.
How to resolve it?

https://image.ibb.co/cOyoNQ/ploop.png
Re: Slow reading speed of ploops [message #52932 is a reply to message #52931] Mon, 28 August 2017 08:29 Go to previous messageGo to next message
khorenko is currently offline  khorenko
Messages: 532
Registered: January 2006
Location: Moscow, Russia
Senior Member
Too many undefined variables:
- what is the ploop state before experiment?
* it may be fresh - so you read the data that was never written - and it requires additional actions to allocate blocks (ploop - is an expandable format!)
* it may be old - then it may be significantly fragmented and random io is slower than the sequential one
- do you measure on the same node?
- what is the system? Kernel version?


Just ad hoc ideas.

Anyway - reading data which was not written by you (test) in advance - is a bad idea for testing.

Suggest following sequence:
# xfs_io -c "pwrite 0 1G -S 0xa -b 1M" -df filename
# xfs_io -c "pread 0 1G -b 1M" -df filename


If your problem is solved - please, report it!
It's even more important than reporting the problem itself...
Re: Slow reading speed of ploops [message #52933 is a reply to message #52932] Mon, 28 August 2017 18:01 Go to previous messageGo to next message
Juves is currently offline  Juves
Messages: 4
Registered: August 2017
Junior Member
ploops are near month old.
Used latest OpenVZ7 OS v7.0.5. Ext4 by default. All placed on one SSD NVMe, same server, node, etc. but different sizes.


Is any same tool for Ext4 for tests?
Re: Slow reading speed of ploops [message #52934 is a reply to message #52933] Mon, 28 August 2017 20:03 Go to previous message
khorenko is currently offline  khorenko
Messages: 532
Registered: January 2006
Location: Moscow, Russia
Senior Member
xfs_io is a generic tool, it can be used for any fs checking.

If your problem is solved - please, report it!
It's even more important than reporting the problem itself...
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