ZFS performance: Extreme low write speed
I am running a small home server. The specs are:
- CPU: AMD Ryzen 5 2600
- RAM: 32 GB ECC
- System drive: 128GB NVMe SSD
- Data drives: 3x 4 TB Seagate Barracuda HDD
The server runs some applications like Nextcloud or Gitea and I want to run 1-2 VMs on it. So there are some web applications, databases and VMs.
The applications and qcow2 images are stored on a raidz1 pool:
$ sudo zpool status
pool: tank
state: ONLINE
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
sdb ONLINE 0 0 0
sdc ONLINE 0 0 0
sdd ONLINE 0 0 0
errors: No known data errors
When I used the applications in the first weeks, I experienced no problems. But since a few weeks I realized extremly low write speeds. The nextcloud instance is not very fast and when I try to start a fresh VM with Windows 10 it needs about 5 Minutes to get to the login screen.
I did some performance testing using fio and got following results:
| Test | IOPS | Bandwith (KiB/s) |
|---|---|---|
| random read | 37,800 | 148,000 |
| random write | 31 | 127 |
| sequential read | 72,100 | 282,000 |
| sequential write | 33 | 134 |
I did some research before posting here and read that I should add a SLOG to the zfs pool for better performance with databases and VMs. But that's no option at the moment. I need to get christmas gifts first :D
But even without a SLOG I don't think these figures are correct :(
Does anyone have an idea? :)
I found the problem by myself.
I saw an article mentioning CMR and SMR. I checked my drives and I realized that I accidentally bought hard drives with SMR :(
I will keep a mirror pool until I replaced the drives with new CMR drives. When I have the new drive I will also use a mirror pool.
Thank you all!