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I set all disks for ZFS so my disk schedule is noop.

You are very confused. I have posted information in this forum about how ZFS works. Lets do it again. Data read: ZFS looks at ARC cache ( for metadata and data ) -> then looks at L2ARC if possible -> then to the pool. You can configure ARC size and set the size for metadata and data in it...

Why noop is bad ?

ZIL - sync write device. ONLY for sync writes. If you don`t have external ZIL - ZFS will use same pool for ZIL ( double write ) How to disable the use of ZIL? #zfs set sync=disabled pool/name/or/sub Why the ZFS write speed outrun disks speed? As I told before write cache. But if you try to...

Are you sure it is for read and write cache? ARC Size: 99.97% 12.00 GiB Target Size: (Adaptive) 100.00% 12.00 GiB Min Size (Hard Limit): 100.00% 12.00 GiB Max Size (High Water): 1:1 12.00 GiB ARC Size...

ZFS ARC cache is for read only. How to manage write cache I still don`t know. You can try to limit IO and speed for VM.

ZFS pool write works by the slowest disk. So in mirror ZFS write speed will be like single disk ( mirror pool can be 2 disks or 10 disks, its not matter ). In your situation ( like I was too ) write speed jumps happens because of ZFS cache in RAM. It can load write data to RAM from application...

Did it really happened to you?

I had ZFS mirror pool of 2 disks and another pool raidz from 3 disks. Both had IO problems. After I upgraded to 2 x raidz2 of 6 disks ( 12 total ) IO problems gone.

Ok sorry found here https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-001.md

Can someone help me and drop the link of git with SACK fix? I can find only RDS fix...

Crontab

Ok but it may be settable permanent to all runs.

make time option controllable from console/GUI for timeout commands.

Don`t know why Proxmox gets timeout but you can add daemonize and KVM will run in background.

Run this comment directly to console (ssh). This is the same command I just removed daemonize option

You don`t need to limit ZIL in size. I just gave you are calculation of recommended ZIL size. It can be larger. How ZIL works? Then ZFS gets sync write request ZFS will put the data to ZIL and into write cache (RAM). After the data is flushed to pool from cache ZFS marks in ZIL about success...

In console #qm showcmd ID Then copy results and try to start VM from console for debugging

ZIL is used for sync write before flushing data to pool. Data flush happens every ~5 seconds. If your system don`t do a lot sync writes then you don`t need huge ZIL. How big ZIL must be? Calculate like this ZIL_MAX_WRITE_SPEED * FLUSH_TIME. What happens then ZFS pool works at max load? ZFS...

OMG sda2 - 512M sdb2 - 512M sdc - 931.5G sdd - 931.5G Is it really the pool size like this?