August 17, 2016, 12:18pm
I have the following configuration:
Physical machine, Quad Core i3-4160, 8GB RAM, Debian Linux, 4x 6TB Western Digital in raidz1
Windows Server 2012R2
Virtual Machine, Quad Core, 8GB RAM, Virtio disks
It looks like the speed is somehow limited to 60Mbit or 6MB/sec when doing a full image backup. Whatever setting I try to change (raw, hashed, compressed, encrypted), I do not see performance improve.
Iperf tells me that I can do around 800mbit of traffic between the client and the server. CrystalDiskMark shows good performance:
I’m suspecting a software issue/setting/limitation somewhere, but I can’t figure out where…
August 17, 2016, 2:54pm
You could try disabling
Run backups with background priority on the clients in the advanced settings on the server. Setting should become active after client service restart.
August 17, 2016, 3:05pm
That is disabled. The service runs with priority ‘Normal’.
Could it be your security software interfering?
August 22, 2016, 8:27am
I will ask my customer if he can think of something. However, I would expect some other process to be using a lot of CPU or something…
I did a fresh install of W7 last week.
The backup was running at about 56kbps over Gb LAN!
It turned out the single core CPU was maxed out by the Windows update client.
I killed the update process and it immediately jumped to about 60mbps…
August 22, 2016, 8:37am
The CPU is pretty much idle. And 60Mbps is way too slow. I would expect 100MB/sec.
I wasn’t impressed with 60mbps myself but it only has a 100mb LAN port.
August 23, 2016, 7:58am
There is no security software in place.
August 23, 2016, 11:15am
I’ve setup a different set of machines to try and replicate the issue.
My setup reaches 30Mbit instead of 60, when doing image-backups. However, filebackups go as fast as you can reasonably expect.
My feeling still is that there is something ratelimiting imaging. Especially since the speed on this setup is about half of what my customers setup does…
August 23, 2016, 1:17pm
It’s probably quite hard to properly pin this down. A first step would be to find out if it is the client or server that is slowing it down.
One thing you could try is having a look at UrBackupClientBackend.exe via
http://processhacker.sourceforge.net/ and then increasing the CPU priority of the image read-ahead thread.
August 23, 2016, 1:39pm
Client, I’m 99% sure.
I’m currently running an incremental image backup. There is almost no traffic between the client and the server, I can tcpdump the stream and keep track of it. It’s mostly keep-alives.
The client keeps running at 3.something MB/sec, also if I change the priority to Realtime and the I/O Priority to High.
I tried Windows Server Backup, btw. To see if that is just as slow with VSS, but that kicks at around 80MB/sc.
August 23, 2016, 1:46pm
That can be normal. It reads the whole disk and sends only changed blocks.
August 23, 2016, 1:48pm
I understand that. But if the server would be a bottleneck, one would expect a lot of traffic between the client and the server. The server is idle…
I am currently waiting for the Windows 8.1 ISO to come in and see if that behaves the same.
August 23, 2016, 1:50pm
The question is if it is the bottleneck during full image backups
August 23, 2016, 1:51pm
Well. I’m seeing the exact same disk-read-speed on the client in an incremental run and in a full backup. So don’t you agree that we can pretty safely assume that it’s the client?
August 23, 2016, 1:55pm
Yeah, my guess is that the read-ahead needs improvement. I just need to make sure that’s the bottleneck and that it is not simply fixed by increasing the CPU priority of the read-ahead thread.
August 23, 2016, 1:58pm
(The normal Windows task manager can’t set thread priorities, Process Hacker 2 can)
August 23, 2016, 3:35pm
Windows 8.1 has about the same performance…