Poojan's Tech Blog

I got my hands on an m550 128GB drive (for around $75 with the recent pre-Thanksgiving/pre-Christmas discounts).

Here are some comparisons between my old ZIL (the m500 128GB) and the new one:

Here are some snippets of zpool isotat output:

No ZIL

m500 128GB as ZIL

m550 128GB as ZIL

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So, you remember that pfSense build that I talked about before? Well, it was drawing around 25 W.

I know, right? Unacceptable!

So, one of the things I tried to figure out is what the main power draw is. The PicoPSU accepts a 12V input. Could the ac/dc adapter be hurting my efficiency?

The adapter I have is a 12V / 5A (60W) adapter that I got for around $10 off Amazon. I figure it wasn’t anything special, and was probably not terribly high efficiency.

I decided to measure the efficiency of the ac/dc adapter. I did this by measuring the power into the adapter with a Kill-A-Watt. And to measure the output power, I used an ammeter (the ammeter function of a multimeter). (I assumed the PSU was delivering 12V; if it was a little low, my efficiency assumptions would be wrong.)

To do this, I had to cut one of the chords on the adapter and place the multimeter in series. (I could alternatively cut the input chord on the PicoPSU, but I figure an adapter is easier to come by than a PicoPSU.) Here’s a picture of how that looks:

Multimeter in series with dc supply chord

And here are the readings on the Kill-A-Watt and multimeter:

Kill-A-Watt reads 20.6 W

Multi-Meter reads 1.64A

Which all means that my efficiency is 1.64A * 12V = 19.68 W / 20.6 W = 95.5%.

I gotta say, I did not expect it to be that high. This is pretty cool. (And a bit surprising, since it seemed like the ac/dc adapter gets pretty warm.)

I should also note that the power draw is less than I remember. I thought it was more like 25A, but I never wrote it down, so I can’t be sure. I’ll take 20A, and be quite happy.

The current on the multimeter bounced around a bit, from 1.6 A to around 1.8 A, but it was well under 2A. Originally, I was interested in getting a (smaller) 2A supply, but I don’t see any need to, with this being so high efficiency. (And who knows, the smaller supply may be lower in efficiency, since they tend to be more compact.)

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Remember back when I was considering a pfSense build? Well, it turns out it was a lot easier than I though.

I realized I could buy (for about $7) an Intel dual-PCI Ethernet card (HP NC7170), and the $6 riser card would allow me to fit it into my case. (I had to do a little bit of metal cutting with a Dremel, since there are no PCI slots in the back of the computer.)

So, that allowed me to get full gigabit speeds off the pfSense. In addition, I’m now* using Intel cards to do so, so that should be better in terms of offloading the CPU.

Here is a picture of this build:

pfSense build with Intel NIC wedged in

Note that the Intel NIC is sort of resting on the ac/dc adapter (which I also stuffed into the case, since I had removed the PSU that came with the case). I later reinforced it (sort of) with zip-ties.

This is something I meant to post earlier, but forgot for a long time. I finally have a free night (where I’m not working), so I thought I’d catch up.

* And since I built this, I’ve changed my setup. I noticed that the PCI card was drawing about 10 watts—meaning, when it was plugged in, I’d see 35 Watts total, and when I removed it, it was 25 watts total. (This is steady-state power, after the router booted up.) So, I went to vlan tagging with a openWRT router, and am using the single gigabit Ethernet that is built-in to the motherboard. At first, I worried about using a Realtek NIC, but I haven’t had a single problem with them. The point with the Intel cards was to offload the CPU, but the higher power doesn’t seem worth it. Finally, I notice that the Alix boards all have Realtek NIC’s.

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I’ve been setting up yet another remote backup lately (see associated problem here). For this purpose (on Unix), the duplicity solution looks ideal. However, I’ve tried it on a couple of lightweight FTP servers (a TL-WDR3600 and a Raspberry Pi) and neither of them work. I keep getting a “Permission Denied” message.

I did quite a bit of investigation, and found that it’s related to the way that duplicity’s FTP backend, ncftp/ncftpput sends files. Or really, a quirk of vsftpd, where it won’t let you put a file with an absolute path (and more specifically a file with a directory name). I’ve seen other reports of this on the Internet here and here.

Here’s a sample ncftpput debug log:

2014-06-25 00:56:34  331: Please specify the password.
2014-06-25 00:56:34  Cmd: PASS xxxxxxxx
2014-06-25 00:56:34  230: Login successful.
2014-06-25 00:56:34  Cmd: PWD
2014-06-25 00:56:34  257: "/"
2014-06-25 00:56:34  Logged in to 192.168.1.2 as Poojan.
2014-06-25 00:56:34  Cmd: FEAT
2014-06-25 00:56:34  211: Features:
2014-06-25 00:56:34        EPRT
2014-06-25 00:56:34        EPSV
2014-06-25 00:56:34        MDTM
2014-06-25 00:56:34        PASV
2014-06-25 00:56:34        REST STREAM
2014-06-25 00:56:34        SIZE
2014-06-25 00:56:34        TVFS
2014-06-25 00:56:34        UTF8
2014-06-25 00:56:34       End
2014-06-25 00:56:34  Cmd: PWD
2014-06-25 00:56:34  257: "/"
2014-06-25 00:56:34  Cmd: CWD folder1/duplicity/Public
2014-06-25 00:56:34  250: Directory successfully changed.
2014-06-25 00:56:34  Cmd: CWD /
2014-06-25 00:56:34  250: Directory successfully changed.
2014-06-25 00:56:34  Cmd: TYPE I
2014-06-25 00:56:34  200: Switching to Binary mode.
2014-06-25 00:56:34  Cmd: PASV
2014-06-25 00:56:34  227: Entering Passive Mode (192,168,1,2,225,89).
2014-06-25 00:56:34  Cmd: STOR folder1/duplicity/Public/duplicity-full.20140625T055614Z.vol1.difftar.gpg
2014-06-25 00:56:34  550: Permission denied.
2014-06-25 00:56:34  ncftpput folder1/duplicity/Public/duplicity-full.20140625T055614Z.vol1.difftar.gpg: server said: Permission denied.
2014-06-25 00:56:34  Cmd: QUIT
2014-06-25 00:56:34  221: Goodbye.


However, I ran a few tests, and I found that if one cd‘es to the directory and then puts (STOR‘es) the file, everything works. My guess this is a chroot-style feature. So, I created a small Python script that will parse the arguments that duplicity sends, and inserts cd (to the target directory) command before uploading the file. This works well. Here’s the script:


#!/usr/local/bin/python3
import argparse
import subprocess
import sys
import os

#cmd_args = ['/usr/local/bin/ncftpput', '-d', 'ftp-debug.log', '-W', 'cd {0}'.format(dest_dir)] +  sys.argv[1:-1] + [dest_file]
cmd_args = ['/usr/local/bin/ncftpput', '-W', 'cd {0}'.format(dest_dir)] +  sys.argv[1:-1] + [dest_file]
subprocess.Popen(cmd_args)


The script is called ncftpput, and is placed in a directory called ~/duplicity_bin. I then add this directory to my path before running duplicity. Here’s a shell script that does that:


#!/bin/sh
export FTP_PASSWORD="XXXYYYXXYXYZY"
export PATH="/home/Poojan/duplicity_bin:$PATH"
duplicity -v 9 --encrypt-key=DEADBEEF full /tank/Users/Public ftp://Poojan@192.168.1.2/folder1/duplicity/Public


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