very slow vms and backup due to very low disk performance (too low FSYNCS)

S

spartakus333

New Member
Apr 26, 2016
8
0
1
46
HI thanks a lot for this excellent project...
Here's my PB
1- my vms are too slow.. can't even open a window while using a rdp access to them
2- a backup of vm of 2GB hard disk size took 8hours !
after a lot Googling I comes with the following conclusions
This is due to the very slow FSYNCS value (40)

Here's my config
1- Server: DELL Power Edge R220 2 controllers NO RAID
pveversion
pve-manager/4.1-1/2f9650d4 (running kernel: 4.2.6-1-pve)

2- lspci | grep SATA

00:1f.2 IDE interface: Intel Corporation 8 Series/C220 Series Chipset Family 4-port SATA Controller 1 [IDE mode] (rev 05)
00:1f.5 IDE interface: Intel Corporation 8 Series/C220 Series Chipset Family 2-port SATA Controller 2 [IDE mode] (rev 05)

Tests done without any VM running

3- hdparm -tT /dev/sda

/dev/sda:
Timing cached reads: 29234 MB in 2.00 seconds = 14633.75 MB/sec
Timing buffered disk reads: 548 MB in 3.00 seconds = 182.38 MB/sec

4- pveperf /var/lib/vz

CPU BOGOMIPS: 24741.56
REGEX/SECOND: 2689348
HD SIZE: 341.08 GB (/dev/mapper/pve-data)
BUFFERED READS: 155.68 MB/sec
AVERAGE SEEK TIME: 24.64 ms
FSYNCS/SECOND: 43.83

Some Indicators that my help
1- I got this problem in proxmox 3.3 and 4.1 with proxmox 2.0 on the same hardaware FSYNS value was much greater (900)
2- as this is a software issue I think this could be due to :
a- some kind of modules integrated to the new kernels
b- some thing related to mounting partitions (lvm may be ) but not too sure as the same test done
on the other disk mounted simply by mount /dev/sdb1 /mnt/sdb1 give the same results

5- pveperf /mnt/sdb1
CPU BOGOMIPS: 24741.56
REGEX/SECOND: 2653792
HD SIZE: 458.32 GB (/dev/sdb1)
BUFFERED READS: 178.99 MB/sec
AVERAGE SEEK TIME: 18.45 ms
FSYNCS/SECOND: 14.79

Thanks a lot for your help
 
Quite normal, because most file system use "barrier=1" as default now (was barrier=0 with older kernels).
 
Thanks a lot for your quick answer, I did the following:

1- remounted my second drive with "barrier=0"
mount /dev/sdb1 /mnt/sdb1 -o barrier=0
2- did the pverperf again
pveperf /mnt/sdb1

CPU BOGOMIPS: 24741.56
REGEX/SECOND: 2709607
HD SIZE: 458.32 GB (/dev/sdb1)
BUFFERED READS: 178.32 MB/sec
AVERAGE SEEK TIME: 20.14 ms
FSYNCS/SECOND: 43.22
DNS EXT: 1030.92 ms

=>same state

1- My main goal is to have my VMs working fine and the backup with a reasnoble duration (not 8hours for 2GB hard drive !) how can I do that ?

2- What do you think about turning back to proxmox 2 as it 's much more performant for disk I/O ?

Thanks a lot for your HELP...
 
Last edited:
spartakus333 said:
HI thanks a lot for this excellent project...
Here's my PB
1- my vms are too slow.. can't even open a window while using a rdp access to them
2- a backup of vm of 2GB hard disk size took 8hours !
after a lot Googling I comes with the following conclusions
This is due to the very slow FSYNCS value (40)

Here's my config
1- Server: DELL Power Edge R220 2 controllers NO RAID
pveversion
pve-manager/4.1-1/2f9650d4 (running kernel: 4.2.6-1-pve)

2- lspci | grep SATA

00:1f.2 IDE interface: Intel Corporation 8 Series/C220 Series Chipset Family 4-port SATA Controller 1 [IDE mode] (rev 05)
00:1f.5 IDE interface: Intel Corporation 8 Series/C220 Series Chipset Family 2-port SATA Controller 2 [IDE mode] (rev 05)
Click to expand...
Hi,
IDE mode is not the mode which you want! Can you switch in the bios to AHCI mode?
Tests done without any VM running

3- hdparm -tT /dev/sda

/dev/sda:
Timing cached reads: 29234 MB in 2.00 seconds = 14633.75 MB/sec
Timing buffered disk reads: 548 MB in 3.00 seconds = 182.38 MB/sec

4- pveperf /var/lib/vz

CPU BOGOMIPS: 24741.56
REGEX/SECOND: 2689348
HD SIZE: 341.08 GB (/dev/mapper/pve-data)
BUFFERED READS: 155.68 MB/sec
AVERAGE SEEK TIME: 24.64 ms
FSYNCS/SECOND: 43.83
Click to expand...
was kind of disks are this? 155MB/s is quite good for an disk. seek time of 24.6 is very bad!
Is the disk busy from other things?

Udo
 
Hi thanks a lot for your answer Udo..

1- I already changed the "IDE mode" to the "AHCI mode" in the bios settings , that changed nothing

2- "seek time of 24.6 is very bad!" I don't now why ?!

- "Is the disk busy from other things?" => there isn't any vm running, just fresh proxmox 4.1 installation

- "was kind of disks are this?" => it's the disk comming with dell R220 server (can't check excatly the model right now)

But seems that the PB comes from the kernel version in proxmox greater than proxmox 2.0

and how the partitions are mounted in proxmox versions after 2.0.

I 've this PB of VMs and disk I/O too slow only in proxmox 3 and proxmox 4

It's really frustratiing to have to go back to proxmox 2 as I saw the cool functions in proxmox 4.2

but really figure out how to fix this PB of too slow disk and low FSYNCS and I tested it in different

hardware, it's always the same results..
 
Last edited:
You must log in or register to reply here.
Top Bottom
Back