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iSCSI speed over S2S VPN

StarWind VTL / VTL Appliance / Storage Gateway for Backblaze

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iSCSI speed over S2S VPN

Postby mga » Wed Dec 04, 2019 10:14 pm

Hi,

We are developing our new backup strategy and we are planning to use Starwind VTL as our offsite backup solution. In this scenario we experience a very pure tape backup speed but I don't have too much experience with iSCSI devices so I'm not sure if this is normal or am I doing something wrong.

In this configuration we backing up servers with a DPM 2019 in our server room to disk. From that disk we planning to create offsite backup to VTL if possible through a site2site VPN to our office where we can easily replace disks behind VTL withouth going physically to the server room.

What I found is:
speedtest.net tells us that the download speed is ~500Mbps and the upload speed is ~460+Mbps in the server room.
In our office we have a 500Mbps download speed and officially 40Mbps upload. Theoretically in this case the office downloads the content so the download speed is the interesting which is fine.
A simple file copy from our server room (from DPM server) to our office has a 165+Mbps speed.
But when I try to use DPM to offsite backup through the same site2site VPN it has a maximum of 24Mbps which is very poor compared to a simple SMB file transfer.
If I use an iSCSI target which is in the same room as our DPM server then its backup speed is also fine (~125-130Mbps).

Based on this the iSCSI config is fine. As the file copy speed and speedtest result are good I think our internet is also good on both side.

I'm not sure what can be wrong. Does anyone has any idea?

Thank you in advance!


Edit: I went through this post and also tested the bandwidth with NTTTCP and iPref tools. The results are over 100Mbps in both case so now I'm sure the net connection is fine.
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Re: iSCSI speed over S2S VPN

Postby mga » Thu Dec 05, 2019 11:16 pm

Ok, I have been looking the documentation since days now and I found that on the GUI management there is an option called "Allow multiple concurrent iSCSI connections". I haven't found a way to set this through PowerShell in the free edition.
Can this be my problem? Is it possible that the VTL uses a single connection by default at for example 23Mbps in our environment? And if I would have multiple parallel connection it could increase the speed over 100Mbps?


https://www.starwindsoftware.com/resour ... vironment/
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Re: iSCSI speed over S2S VPN

Postby yaroslav (staff) » Fri Dec 06, 2019 3:42 pm

Speedtest workloads are not the same as during file copy. While copying the file, the network bandwidth is altered by a bunch of facts. Here is the article on what bottlenecks file copy performance: https://blogs.technet.microsoft.com/jos ... o-instead/, https://pomfort.com/article/determine-c ... -software/.
If I get it right, most of the time you are going to transfer the backups to your office. Since you do not want to run to the server room, why have the disk as a milestone between the data source (DPM) and your office servers? According to StarWind VTL best practices (https://www.starwindsoftware.com/best-p ... /?pdf=1402) there are 2 VTL configuration scenarios:
1. Backup software and VTL are installed on one physical server with Storage Repository connected. It is the so-called “all-in-one-box” scenario. Say, you have the VTL running on the same server as DPM 2019 which also serves as the backup repository. Simple.
2. Backup software is installed inside a VM in (i.e., the host in the server room) or outside (say, the servers in your office) the cluster; VTL, in turn, is installed on the storage repository host (the servers in your office). Here you have data flowing to the DPM 2019 host and sent to VTL. Secure.
You could upload the data arriving from DPM host to your office, where you have a VTL instance running. Do little configurations with iSCSI Initiator – namely, add there the path to the DPM server – and enjoy 125-130+ Mbps speed.
Now, I’d like to answer your second post. The option “Allow multiple concurrent iSCSI Connections” is in VTL not for performance concerns. This option allows for multiple initiators (i.e., servers) to talk to a single target (i.e., tape). And, this option is enabled by default.
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Re: iSCSI speed over S2S VPN

Postby mga » Mon Dec 09, 2019 12:12 am

Hi there,

Thanks for your answer and the info.
Finally fortunately I had two simple issue. Once I rebooted the server where VTL was installed the upload speed immediately jumped up to ~45Mbps. I haven't made any changes I just couldn't reboot the server earlier.
The second was my fault. I made a lot of tests. During this I created a lot of settings and unfortunately when I did the measure I missed to increase the allocated drives for the protection group in DPM. Immediately when I set it 4 I reach 150+Mbps through my S2S VPN which is absolutely fine for me.

Thank you again!
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Re: iSCSI speed over S2S VPN

Postby yaroslav (staff) » Mon Dec 09, 2019 8:30 am

We are always here to help you.
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