Sunday, July 08, 2012

DroboFS, so slow. NFS Slower.

Two years ago I got a DroboFS because I wanted extra storage accessible to the whole family, a place to keep Time Machine backups, easy hotswap maintenance, and no hassle with plugging in any directly attached storage devices. The Drobo FS can do all this, but it is so slow, I hardly ever use it. Whenever I do try to use it, it is such a slug, I almost always get sidetracked starting to research something to replace it so I can get rid of it. Like this guy.

Using the DroboFS over 802.11n (2.4Ghz, n-only) wireless, it reads and writes at about 5MB/s (megabytes per second). This is under OSX 10.7.4 Lion, the most recent Drobo firmware 1.2.4, and all Western Digital 2TB EARS "green" drives. It's about the same speed when the base station is set to n plus b/g compatibility. In my house, the n-only 5Ghz was worse.

I have read that the best DroboFS will ever do is about 30MB/s (megabytes per second, or 240 megabits per sec), which is 6 times faster than what I am getting out of it over wifi. Sometimes I would be willing to plug in to ethernet to get things moving faster, but that's not very convenient on a Macbook Air with no ethernet.

The Apple Airport Extreme Base Station that I have is from 2008 and can do "802.11n" according to the draft specification that there was at the time. That should mean wireless speeds of up to 160mbps (20 megabytes per second). However, I have never seen it go faster than "g," which is a maximum of 54megabits/sec (6.75MegaBytes/sec). I know this because iStat Menus gives me nice little speedometers in the menubar that I am always checking. If my base station is too old to get real world "n" speed, then I am within 1MB/s of what the hardware can push and it's not Drobo's fault that it's  practically unusable over wifi. But, assuming that I can get "n" wifi speed, there are 15 more megabytes/second (3 times faster) that I should be able to read from/write to it.

While trying to find out whether there was any way to make it faster, I read that some people found some performance gain using NFS, as opposed to the built-in AFP protocol. In order to try it, you have to enable DroboApps, and install the unfsd. I did that and found NFS is even worse than AFP, losing about 1MB/s in both read and write speed.

In order to get NFS to even work at all, I had to read a lot of blog posts. The default exports file that comes with the unfsd app offers to share every share created in the Drobo Dashboard:


and uses the "no_root_squash" option, which means that files created over NFS get done on the Drobo system as the root user. That is usually not good, and usually the opposite of how any software would generally come by default.

In order to connect to this NFS export you can either get to the Finder and choose "Go, Connect to Server" from the top menu (Command + K) and type:

nfs://[IP address of DroboFS box]/mnt/DroboFS/Shares/

(Notice that the path on the end of that connection string is the entire full path to the share from the perspective of the Drobo box. It won't work if you put the share name alone after the IP address.)

Or you can manually mount the export from a shell prompt. Before mounting this way, you have to make an empty directory as the spot that you will mount it on top of. So, first:

mkdir ~/myDroboshare

sudo mount -w -t nfs /Users/[your username on your Mac]/myDroboshare

all the above has to be typed on 1 line.

If you do one of the above, then you'll find the share accessible to OSX and can see it in Finder windows, and from a shell prompt you will be able to write in there. But from the GUI, everything will appear as a read-only filesystem. GUI apps will think they cannot write in there and give you error messages.

In order to fix this problem, you need to get back to the Drobo box and edit the file that is in the same directory as the exports file (/mnt/DroboFS/Shares/DroboApps/unfsd/) and add in a "-s" for "single user mode" to this line:

${prog_dir}/unfsd -s -e ${exportsfile} -i ${pidfile} >> ${logfile} 2>&1

After editting the file, you want to restart the nfs service on the Drobo box. The best way to do that is by running that script from a shell prompt on the DroboFS box:

/mnt/DroboFS/Shares/DroboApps/unfsd/ restart

In order to do it that way, you will have to have installed the Dropbear SSH app, and ssh into the box as root. Otherwise, the only way to restart any of these DroboApps is to restart the whole DroboFS box, by turning it off and on, or using the "restart" button in Drobo Dashboard under the "Tools" menu.

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