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This is just a quick question to check file IO relative performance in Azure. My client has a small three-VM set-up: domain controller, file server and XenApp application server - connected via a virtual network. They are experiencing slow access between the XenApp and file servers, specifically in Sage.

They don't have a support contract with Microsoft and before I suggest they sign up for one, I thought I'd ask here to verify my summary there is something wrong.

On the XenApp server, there is the C: drive (on SSD) and the temporary D: drive (local storage on physical host I think). A 4GB copy between the D: and C: drives and it runs at ~20MB/s. Not stellar performance but kind of acceptable.

However, copy the same 4GB file across the virtual network to the file server, and they are getting a pretty useless 600KB/s. Hence the reason Sage is slow - it's a traditional client/server program pulling data from the database.

Even on my low-grade home network between my PC and Windows server over 1Gbps network, I get ~100MBps... the two VMs in question have allegedly 40Gbps virtual network cards.

Am I correct in saying that this 600KB/s copy speed is many factors slower than one can expect?

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Rob Nicholson
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  • Is the XenApp server hosted in Azure, or somewhere else? – John Mahowald Jul 25 '19 at 12:27
  • Please edit your question to give more details regarding the file server. For example: is the file server an actual VM with attached disks? (if so: what type of disks: SSD? Standard? This makes a big difference). Or is your file server an Azure File Share Service instance? (if so: what type: Standard? Premium? Huge difference in performance between the two) – David Makogon Jul 25 '19 at 20:48
  • All three servers are hosted on the same Azure data centre – Rob Nicholson Jul 25 '19 at 22:50
  • I don't think that level of detail is needed to answer this question - is a file copy speed of ~600KB/second normal across two Azure file servers normal? I know the underlying disks can make a big difference but heck, even USB-2 pen drives can handle 20MB/s! – Rob Nicholson Jul 25 '19 at 22:52
  • I've almost answered my own question with some more detailed testing today. Something is very wrong with the file server in terms of IO speed. Confirmed by copying the same file to the domain controller which is on the same Azure virtual LAN. That copies at a much more acceptable 40MB/s - 80 times faster than the copy to the file server – Rob Nicholson Jul 25 '19 at 22:54
  • I have edited the title to reflect more what I'm asking - not looking for specific speed estimates or questions about underlying disk types - just whether that ballpark speed is way, way too low (and it is) – Rob Nicholson Jul 25 '19 at 22:57
  • For reference, this details the speeds on can expect from a standard HDD on Azure. And yes, 60MB/s would be perfectly acceptable for this application https://docs.microsoft.com/en-gb/azure/virtual-machines/windows/disks-types#standard-hdd – Rob Nicholson Jul 25 '19 at 23:12
  • I'm think I'm going to answer this ticket myself saying "No, that's not normal :-)" as I'm just trying to download a 1GB test file from https://www.thinkbroadband.com/download and even that is giving an ETA of 1 hr 45 mins which is about the same as when I copy from the other server. I've not yet managed to get a 1GB file to copy to this server - it drops out of the copy... I may raise another question about how one might go about diagnosing this one as that slow download speed points the finger at a slow network interface – Rob Nicholson Jul 25 '19 at 23:16
  • Final comment this evening - it's the write speed that's very slow. Copy from file server to XenApp server temporary drive and acceptable 40MB/s. Copy same file back the other way (writing to file server) and speed drops to 500KB/s – Rob Nicholson Jul 25 '19 at 23:38
  • @RobNicholson - why are my questions not relevant? You have given no details at all about your file server. If you are using regular (non-SSD) disks, your IO is limited in terms of bandwidth and throughput. Premium disks are far more performant, as are locally-attached disks. Without that detail, it's impossible to know why your file server is running slowly. – David Makogon Jul 26 '19 at 13:14
  • @RobNicholson - we also don't know what utilization you have, on your file server VM (perhaps you picked a small SKU?) – David Makogon Jul 26 '19 at 13:18

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Basic answer here is no, a file copy speed of 600KB/s is not normal for a copy from one Windows server to another on Azure. There is something amiss with our file server when writing. Reading files is fine - healthy 40-50MB/s.

Rob Nicholson
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