ext4, fstab, io wait

[camaran]

Hi, what's the best fastab setting for ext4 and low io wait?

 

[tom]

as long as you do not have a real reason for changes, use defaults.

if you change defaults, you need to sure that the settings are suitable for your hardware and needs.

 

[camaran]

i have raid software with default setting i have a long io wait time

 

[LnxBil]

What is "long" to you and how did you measure it?

Please post pveperf

 

[camaran]

CPU BOGOMIPS: 38398.64
REGEX/SECOND: 2087224
HD SIZE: 19.10 GB (/dev/md2)
BUFFERED READS: 90.90 MB/sec
AVERAGE SEEK TIME: 13.46 ms
FSYNCS/SECOND: 16.16
DNS EXT: 21.89 ms
DNS INT: 7.68 ms

 

[LnxBil]

Wow ... that is terribly slow.

I see you're using software raid, that could be one of the problems. Please check the io response times on each disk individually.

Besides: You're running Proxmox VE in an unsupported environment if you use software raid.

 

[mmenaz]

Try to mount the file system with "nobarrier" option, a bit more risky (search about the implications) but definetely your fsync numbers will increase a lot

 

[camaran]

i have this

/dev/pve/data   /var/lib/vz     ext4    defaults,nobarrier      1       2

it's ok? or i must use only

/dev/pve/data   /var/lib/vz     ext4    nobarrier      1       2

 

[mmenaz]

i have this

/dev/pve/data   /var/lib/vz     ext4    defaults,nobarrier      1       2

it's ok?

Seems so, I've also noatime, i.e. my config is usually like that

/dev/pve/data /var/lib/vz ext4 defaults,noatime,nobarrier 0 1

of course after changes in fstab you have to remount or better reboot

 

[camaran]

i must restart server for read any changes?

 

[maxprox]

i must restart server for read any changes?

yes! ;-)
EDIT:
have a look at the next post...

 

[udo]

i must restart server for read any changes?

Hi,
no - you can use the flag remount.

Like

mount -o remount,noatime,nobarrier /dev/pve/data /var/lib/vz

control with "mount" before and after that.

Udo