Inconsistent file copy on Windows + ZFS

liim

New Member
Dec 8, 2024
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We have recently run up against an issue where large (>4GB) copies cause lockups within a Windows guest. These can be copies within the same folder, or across disks. The original issue was seen on a RAID Z-1 pool (6x 870 EVO SSD), but has been replicated on ZFS RAID-1 pool with Micron 7450. The issue is not so much the speed (drop-off is expected after the cache exhausts), just the lock-up behaviour with hitting 0bytes/s
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Vm is running on recommended v1.271 virtio drivers and latest Windows Server 2022. Disks have been tested with both virtIO scsi and sata emulation. VM conf below:
Code:
agent: 1
bios: ovmf
boot: order=sata0
cores: 24
cpu: x86-64-v4,flags=+aes
efidisk0: local-zfs:vm-100-disk-0,efitype=4m,pre-enrolled-keys=1,size=1M
machine: pc-q35-10.0+pve1
memory: 8192
meta: creation-qemu=10.0.2,ctime=1758721753
numa: 0
ostype: win11
sata0: local-zfs:vm-100-disk-1,size=200G
sata4: local-zfs:vm-100-disk-3,size=1500G
scsihw: virtio-scsi-pci
smbios1: uuid=d611609a-1d86-461e-a1d7-a56dbbb865b4
sockets: 1
tpmstate0: local-zfs:vm-100-disk-2,size=4M,version=v2.0
unused0: local-zfs:vm-100-disk-5
unused2: local-zfs:vm-100-disk-4
vmgenid: b2156e6c-0295-44ae-8162-e6cee0b8e59c

Attached is a txt file with /proc/spl/kstat/zfs/arcstats and arc_summary. Happy to try tuning options if there are some good first points of call.
 

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