High IOLoad, Slow Diskspead

[TechLineX]

Hello,

since the new installation, we use 2 nodes in a cluster. We have 3 disks on 1 host in an raid0, should be enough speed.
Installations in KVM-Guests are very slow, the server shows always a IO-Delay between 5 and 10%.

iotop:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 2.50 M/s
Actual DISK READ: 0.00 B/s | Actual DISK WRITE: 1657.38 K/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
755 be/3 root 0.00 B/s 11.62 K/s 0.00 % 99.99 % [jbd2/md4-8]
26704 be/4 root 0.00 B/s 302.05 K/s 0.00 % 11.66 % [nfsd]
26703 be/4 root 0.00 B/s 391.11 K/s 0.00 % 8.13 % [nfsd]
26702 be/4 root 0.00 B/s 406.60 K/s 0.00 % 1.55 % [nfsd]

I only use KVM
no cache, raw format

2,50M/s should't be a problem for a raid 0. Any ideas? Using the newest version of Proxmox.

Regards

 

[LnxBil]

First: Never, ever use RAID0, never! It's not redundand and should therefore not be called RAID. It's a recipe for disaster.

Depends on the kind of access. If all access is random 4K write blocks without any controller caching leads to approximately 400 KB/sec for a simple 7.2k SATA drive (https://en.wikipedia.org/wiki/IOPS#Mechanical_hard_drives).

It seems that you use RAW on ext4 or did you use LVM? Don't use RAW on ext4, use RAW on LVM.

 

[TechLineX]

I use RAW at ext3

regards