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Now we live in a world where computers with decent sized hard drives are hard to come by, I'm often tasked with rationing the internal drives on our fleet of computers. A priority that I was happy to bid farewell to 15 years. What is old is new again...

Anyway, a key target for offloading to an external drive are the hundreds of gigabytes of virtual machine images we tend to use regularly. We recently deployed a shiny new NAS (Synology DS418) and have been making great use of it.

In my first bog-standard attempt to use the NAS for VM storage, the results were unacceptable. My criteria for acceptance would be, say, a fresh Ubuntu 18 install booting in less than 10 minutes. Currently I've left it overnight and it still hasn't made it to the desktop.

This is the current setup:

  • Synology DS418 NAS with 4 HDD all in a SHR (Synology Hybrid Raid).
  • NAS connected via Gigabit Ethernet to switch with link aggregation. 120MB/s write performance is pretty typical over Ethernet.
  • Latest VirtualBox running on Macbook Pro Early 2013.
  • VirtualBox image stored on NAS, mounted as a network share via SMB.
  • VirtualBox pointed to a symlink that points to the network share.
  • Macbook connected to switch via WiFi at 217 Mbps link speed.
  • Running fresh Ubuntu 18 install from within VirtualBox.

As mentioned, the results are poor. Far poorer than I expected. Obviously there are many things to tweak (starting with Ethernet), but given that it's a many-day affair to test (have been waiting for Ubuntu to shutdown for nearly an hour now) I was hoping others could share their experience or prediction - do I have a hope of achieving my criteria of "acceptable" or is there something fundamentally wrong here?

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  • Wifi is a bad choice for this, 217Mbps is about 27MB/s. Move to wired 1Gb Ethernet. Are you sharing this NAS? What RAID level, unless it's 10, that will negatively affect your performance. Best solution would be a single 1TB SSD attached locally via Thunderbolt which will give you very usable performance.
    – essjae
    Commented Sep 11, 2019 at 23:14
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    I work with vm’s in a non-production environment stored on a simple NAS over gigabit Ethernet and it works great. Clearly taking a day to boot indicates something is seriously wrong, not just slow. You can’t run virtual machine storage over WiFi. It just isn’t going to work. One little hiccup and the whole thing is going to freak out and WiFi is far too unstable.
    – Appleoddity
    Commented Sep 11, 2019 at 23:22
  • @essjae thanks but as explained in the question I'm not interested in a 5x speed boost. The NAS details including RAID are in the question. The best solution doesn't answer my question.
    – Heath Raftery
    Commented Sep 11, 2019 at 23:43

2 Answers 2

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From the OP.

As suggested by Appleoddity in the comments, WiFi is a potential showstopper. Sure enough, I switched to Ethernet and the difference was stark. Performance is staggeringly good - booting, downloading, installing large software packages, shutting down. For example, booting Ubuntu18 takes less than a minute, using a browser to download files runs at ~10MB/s. All functions are fast enough to be no discernibly different to having the VM stored locally.

However, there may have been some confounding factors - the original Ubuntu image started showing various software package issues and eventually would not boot to the GUI and was missing critical tools. I ended up re-installing from scratch. I'll never know whether the damaged install was a symptom or a cause, but it was certainly related.

There are very few occasions I would resort to WiFi. Here's one more reason why not.

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I don't do a VM across a network share, but I do have myself and multiple students booting the Ubuntu ISO image off network/PXE on gig ethernet. The actual file share portion is handled via NFS. Very workable as long as boots are somewhat staggered across 15 of us. Once we are up and running it is actually more responsive than loading new data off the CD when larger programs (firefox, open office) are launched.

Also, I've seen slowness like you describe in VirtualBox when running on local hardware (7200rpm disk) when you create a 64bit VM but load a 32bit OS in it. Just getting to the "select groups of packages" part of the Debian install on a netinstall disk took almost an hour. While this works fine for real hardware it doesn't work so well in VirtualBox.

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