Windows 10 VM sudden speed drop when copying files

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tilenb

New Member
Apr 30, 2022
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Hi I have a problem with my win 10 vm that when copying files, it copies at a good speed 200-400MB/s and then randomly drops to 0, and all other vms become unresponsive, also the I/O delay becomes really high. It's the same if I'm copying from a network drive or like a folder from destkop to any other folder on the system, and it happens both with large and small files. The drives for the store are two mirrored Crucial MX500 1TB SSD's.
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VM config:
bios: ovmf
boot: order=ide2;scsi0;net0;ide0
cores: 6
cpu: host
efidisk0: local-zfs:vm-112-disk-0,efitype=4m,pre-enrolled-keys=1,size=1M
hostpci0: 0000:06:00.0,pcie=1,x-vga=1
hostpci1: 0000:06:00.1,pcie=1
ide0: none,media=cdrom
ide2: none,media=cdrom
machine: pc-q35-6.1
memory: 16384
meta: creation-qemu=6.2.0,ctime=1661160438
name: CloudGamingW10
net0: virtio=56:C5:F2:35:D1:56,bridge=vmbr0,firewall=1
numa: 0
onboot: 1
ostype: win10
scsi0: local-zfs:vm-112-disk-1,cache=unsafe,discard=on,iothread=1,size=256G
scsihw: virtio-scsi-pci
smbios1: uuid=fc41ae73-e149-4ec5-9c95-ea1b39bd36af
sockets: 2
vmgenid: d168d596-db2b-4d33-92ef-2251af62bbd8
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Any help would be greatly appriciated!
 
Beside using cheap consumer SSDs(enterprise SSDs are highly recommended with ZFS) you also use "cache=unsafe". So next power outage your whole disk might be lost. So I hope you got your PVE server behind a UPS. And recommended cache option for ZFS would be "none".

But yeah, that performance drop is probably your real SSDs performance. You only see the good performance because of RAM/SLC caching and as soon as the caches get full you drop to real performance.
 
Dunuin said:
Beside using cheap consumer SSDs(enterprise SSDs are highly recommended with ZFS) you also use "cache=unsafe". So next power outage your whole disk might be lost. So I hope you got your PVE server behind a UPS. And recommended cache option for ZFS would be "none".

But yeah, that performance drop is probably your real SSDs performance. You only see the good performance because of RAM/SLC caching and as soon as the caches get full you drop to real performance.
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Yeah I've put it at unsafe because I was testing if there would be any difference. So you're basically saying I have shit ssd's and only thing I can do is replace them?
 
If your aren't happy with the write performance you got after the drop, then yes. But enterprise SSDs aren't just about performance. They are rated for 3-30 times the durability, will have a way lower write amplification and your data won't corrupt that easily because of powerloss protection.
 
Dunuin said:
If your aren't happy with the write performance you got after the drop, then yes. But enterprise SSDs aren't just about performance. They are rated for 3-30 times the durability, will have a way lower write amplification and your data won't corrupt that easily because of powerloss protection.
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Could you recommend some drives I could use? That preferably don’t cost a fortune haha.
EDIT: I have a 8x 3TB raid-z3 SAS array in virtualized truenas, I've made a share and added it to proxmox and moved the drive there and it works really really good lol. Still I'm open to ssd suggestions.
 
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With SSDs you basically get what you pay. You shouldn`t look at the price per TB of storage but at the price per TB of TBW. Then you will realize that even a 1000€ enterprise SSD might be a bargain. Your 48€ 500GB MX500 for example only got a TBW of 180TB. A 480GB Intel S4620 for 273€ got a TBW of 4200TB. So you pay 5.6 times the initial price but the SSDs is build to handle 23 times the writes. If you see it this way, that MX500 is way too expensive for the durability you get.

If you are low on budget search ebay and so on for second hand enterprise/datacenter SSDs. They are build way more durable, so even a SSD heavily used over many years might still survive longer than a new consumer SSD and you get them for the same price. Best you ask the seller before buying to send you a SMART output of it. So you can see how much that SSD is worn off and decide if it is a good deal or not.
 
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