[SOLVED] once again: Poor FSYNCS/SECOND with mdadm/LVM

[sherminator]

Hi,

my hardware is:
- HP ProLiant DL370 G6 with 24x 2,5" hot swap bays (3 backplanes)
- these backplanes are connected to an HP SAS Expander Card
- the Expander Card is connected to an Avago SAS 9211-8i HBA
- 22x HP SAS HDDs (300 GB, 10k rpm)
- these HDDs are organized as a raid10 via mdadm: /dev/md1
- /dev/md1 is configured as a physical volume and a volume group (vg1) inside - which Proxmox uses for storing vm disk images

For testing purposes I created a logical volume called pveperftest, formatted it as ext4 and mounted it to /mnt.
Finally I ran pveperf:

# pveperf /mnt/
CPU BOGOMIPS:  76773.20
REGEX/SECOND:  1079516
HD SIZE:  98.31 GB (/dev/mapper/vg1-pveperftest)
BUFFERED READS:  1181.28 MB/sec
AVERAGE SEEK TIME: 4.60 ms
FSYNCS/SECOND:  80.40
DNS EXT:  37.82 ms
DNS INT:  1.09 ms

BUFFERED READS looks good, but FSYNCS/SECONDS looks bad, doesn't it?
What can I do to improve this?

My Proxmox ist up to date from the subscription repository:

# pveversion
pve-manager/4.1-5/f910ef5c (running kernel: 4.2.6-1-pve)

The initial setup I did with a Debian installation, not with the Proxmox-ISO.

Thank you very much and greets
Stephan

 

[tom]

mdraid is a not supported setup and there are reason for this.

there are performance and data security concerns, especially if your disks start dying or if you lost power of a disk you can loose data.

therefore we recommended hardware raid or zfs. if you use mdraid, you have to accept the issue above.

 

[sherminator]

Hi Tom,

thanks for your answer!

mdraid is a not supported setup and there are reason for this.
there are performance and data security concerns, especially if your disks start dying or if you lost power of a disk you can loose data.

What a pity! Till today I thought mdraid is a good piece of software.

therefore we recommended hardware raid or zfs. if you use mdraid, you have to accept the issue above.

I don't like hardware RAID anymore, because it's hardly "live scalable". Maybe I give ZFS a try.

Many greets
Stephan