Formating suhe a zvol with an ext4 fs is not working.
Post by Dead Horse
I use ZOL as a back end to my ovirt storage domains, which are accessed
via NFS. I spent some extensive time testing the best way
to achieve maximum throughput to KVM based VM's with ZOL. My storage
inter-connects are multiple port-channeled 10GB links on a 10GB switch
stack between the VM hosts and my ZOL storage. My zpools on each storage
node consist of anywhere from 24 disks to 48 disks (multipathed). Each
zpool has two low latency SSD striped and acting as an L2ARC and two more
acting as a striped and acting as the ZIL.
I found that using ZVOL's formatted with ext4 with a larger blocksize
yielded the best performance when combined with KVM and RAW thick or thin
provisioned file backed disks.
- I create a zvol as follows (Example): zfs create -V 100G -o
- After that a simple mkfs.ext4 -L <zvolname> /dev/das0/foo
- mount command (Example) mount /dev/das0/foo /some/mount/point -o noatime
- /some/mount/point is exported via NFS v3
- You can enable NFS async for additional performance however with the
understanding on the implications of doing so
Additionally the qemu/kvm VM disk cache policy set to none with the IO
policy set to threaded.
Post by Jerome
I'm experiencing strange issue with last version (11) of ZoL.
I don't know if it related with this specifi version as I haven't tried
I created a Linux (debian 64b) box with 35To (raid5) device (presented as
/dev/sdX). On this device I created a zpool.
On this Zpool I have created zfs filesystem shared via NFS (using 1Gbps
ethernet card) to Hypervisors hosts (XenServer / VMware) in order to test.
ZFS does not have any compression or deduplication activated.
* pool: XXXXX*
* state: ONLINE*
* scan: scrub canceled on Tue Nov 6 10:26:30 2012*
* NAME STATE READ WRITE CKSUM*
* local ONLINE 0 0 0*
* sdc ONLINE 0 0 0*
*errors: No known data errors*
On this storage each hypervisor create vhd or vmdk files (sparse files).
Each file is attached as block device disk to Virtual Machines.
In these virtual machine I encounter very low peformance when writing
We experience near 5-10MB/s rate.
Doing the same to an ext4 fs on the same server provides near 90MB/s data
As anyone experienced this ?
Do you have any idea on what is going on ?
Thanks for your help