Nfs – How to get decent NFS performance for workloads like git

nfsshared-storagevagrantvirtualbox

I manage a vagrant setup for our developers running OSX to manage VirtualBox systems for development.

In order to support inotify inside the linux machine, we eschew the usual method of sharing directories with VirtualBox: instead, the Virtualbox machine exposes an NFS share, which is mounted in OSX.

Git (and related tools like sourcetree) are run in OSX, on the shared directory. The performance of this is extremely poor: it often takes up to 5 seconds just to run git status. Cloning a small repository into the mounted NFS drive can take a couple of minutes (5-10 seconds on a local drive).

Obviously NFS performance will be worse than writing straight to a local SSD, but the NFS is just running over a virtual private network interface with Virtualbox.

I ran a couple of benchmarks. The first:

dd if=/dev/zero of=test bs=16 count=16384

Each result is based on 100 samples.

# local drive
Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
0.990   1.000   1.020   1.021   1.030   1.130

# on the shared NFS drive
Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
6.000   6.278   6.390   6.482   6.570   7.630

# inside the VirtualBox instance
Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
0.3600  0.4800  0.5150  0.5552  0.5400  1.4500

The second benchmark:

ioping -c 500

local avg: 6 microseconds
local IOPS: 65.5 k

NFS Latency avg: 703 microseconds
NFS OPS: 1.4 k

Clearly some latency is inevitable, but this is bad enough that it makes some simple tasks quite painful.

The owner of the volume is running Ubuntu 12.10 (Quantal), with default settings. The system mounting the volume is running OSX Mavericks.

At the moment the main nfsd connection is running over UDP, which seems ideal over a virtual connection. I'm not sure whether statsd and lockd are running over TCP and UDP.

I tried mounting with the async flag, and with rwsize boosted, and it made little difference.

What opportunities are there for seriously improving the performance of NFS in this environment?

Best Answer

Try to use this Git setting, which makes a huge performance difference on NFS shares:

git config core.preloadindex true

Quote from the documentation available at: https://git-scm.com/docs/git-config#git-config-corepreloadIndex

This can speed up operations like git diff and git status especially on filesystems like NFS that have weak caching semantics and thus relatively high IO latencies. When enabled, Git will do the index comparison to the filesystem data in parallel, allowing overlapping IO’s. Defaults to true.

Related Topic