FreeNAS + rsync to ZFS + AFP filesharing = bad idea

Unicode (as UTF-8) is a very popular format for encoding filenames on disk, but there are some subtly incompatible variants around. In particular, different operating systems have different ideas about how accents should be handled.

Mac applies something called NFD to filenames before they are stored on disk (Normalization Form Canonical Decomposition). This means that a character like the “ū” in the word “Jingū” is stored as two Unicode characters – a plain old LATIN SMALL LETTER U character, followed by a COMBINING MACRON character:

ls | grep 2009_11_03 | od -c -tx1

0000000    2   0   0   9   _   1   1   _   0   3       M   e   i   j   i
           32  30  30  39  5f  31  31  5f  30  33  20  4d  65  69  6a  69
0000020        J   i   n   g   u    ̄  **  \n
           20  4a  69  6e  67  75  cc  84  0a

Windows does the exact opposite (NFC), combining the “u” and the macron together to produce a single LATIN SMALL LETTER U WITH MACRON character.

0000000    2   0   0   9   _   1   1   _   0   3       M   e   i   j   i
           32  30  30  39  5f  31  31  5f  30  33  20  4d  65  69  6a  69
0000020        J   i   n   g   ū  **  \n
           20  4a  69  6e  67  c5  ab  0a

On Linux, I’m not sure if there is a standard, but it’s typical to find filenames encoded with NFC. If anything, the standard in Linux is that a filename is just a series of bytes and the OS shouldn’t try to mangle them by converting the characters with NFC or NFD normalization forms.

I recently set up a second computer as a FreeNAS 9.2.0 storage device, and I wanted to migrate the files from my MacBook to it. The most straightforward way to do this is to enable the Apple “AFP” network filesharing service on FreeNAS, then on the Mac, copy the files to that network share however you like. This automatically takes care of any character conversion for you.

However, I tried this and only achieved about 2MB/s transfer speeds. I would have died of old age before I would have been able to copy my terabytes of data to FreeNAS.

So, instead I used rsync to send my files directly to the ZFS storage on FreeNAS, bypassing any of its network file system protocols. This achieved a steady ~110MB/s, which is wonderful. The issue came when I went to read those same files over AFP: I could briefly see folders that contained accents in the finder, but they would disappear after several seconds, then reappear 10 seconds later, then disappear again!

The issue was that rsync, being Linux-oriented, preserves the filename encoding when sending files, so the filenames on FreeNAS ended up still in Mac’s NFD format (with accents encoded as separate characters). This is a problem because netatalk, the AFP server on FreeNAS, expects filenames on FreeNAS volumes to be encoded in the “vol charset” which is defined in its configuration file:

http://netatalk.sourceforge.net/3.0/htmldocs/configuration.html#charsets

FreeNAS doesn’t set this explicitly, so it defaults to “UTF8”. Although the netatalk manual doesn’t say it, “UTF8” actually implies “UTF8 in NFC form”, so netatalk will be unable to serve the NFD-encoded filenames that originated on my Mac correctly. What happens is that a MacOS X client lists a directory over AFP, so netatalk converts the filenames on disk (that it thinks are NFC) to NFD (a no-op, since we’ve actually put NFD filenames on there to start with). This allows the accented characters to show up properly in MacOS and the listing looks okay. But then MacOS’s finder asks for more information about a file specifically by name. Netatalk converts the NFD filename that MacOS provides to the vol charset (set to NFC form), and then tries to look it up on the filesystem. But the filename doesn’t exist on the disk in NFC form, so it can’t find the file. This causes the file to disappear again in MacOS’s Finder.

Here are three ways of solving the problem, in order from worst to best:

Option 1: Change vol charset to UTF8-MAC

Changing the vol charset to “UTF8-MAC” will fix the issue by letting netatalk know that the filenames on disk are in NFD form.

The “vol charset” setting is found in the afp.conf file at /usr/local/etc/afp.conf. But you shouldn’t edit this file, as it is automatically regenerated at various times by the script /usr/local/libexec/nas/generate_afpd_conf.py. Instead, edit that script:

# Remount root as writable so we can edit the script:
mount -uw /
nano /usr/local/libexec/nas/generate_afpd_conf.py

Find this section:

cf_contents.append("\tmax connections = %s\n" % afp.afp_srv_connections_limit)
cf_contents.append("\tmimic model = RackMac\n")
cf_contents.append("\tvol dbnest = yes\n")
cf_contents.append("\n")

Before the append("\n") line, add:

cf_contents.append("\tvol charset = UTF8-MAC\n")

Save and exit, then:

# Remount root as readonly and commit our changes to disk (takes ages on a USB flash drive, so be patient)
mount -ur /

Now on FreeNAS’s Services/Control Services page, turn AFP off and back on in order to regenerate its configuration file. You should see the new line added when you cat /usr/local/etc/afp.conf. Your Mac-encoded filenames will now serve correctly through AFP!

Option 2: Change the encoding of the filenames on FreeNAS’ disk to NFC

Alternatively, you could leave the AFP configuration alone and change the filename encoding on disk instead. This will make the files available to Mac, but with the caveat that the filenames will no longer be the same as your source files due to the encoding difference, and rsync that runs directly against ZFS will no longer consider them to be the same files.

I did this by creating a new plugin jail, then adding my ZFS volume as additional storage to that jail. From that jail’s console button, I used “pkg install convmv” to install the convmv package, which can change filename encodings. I changed the encoding to NFC like so:

convmv -f utf-8 -t utf-8 --nfc -r --no-test /mnt/my-files

(You should run without –no-test first so convmv can tell you exactly what it plans to do, before you accidentally mangle your filenames more!)

Option 3: Go back in time and copy the filenames correctly in the first place

You can avoid this whole issue in the first place by having rsync convert the filenames to NFC as they are copied to ZFS:

rsync -a --iconv=utf-8-mac,utf-8 my-files/ root@freenas.local:/mnt/my-files/

In fact, if you fix the filenames using Option 2, then do all your future rsyncs with the character conversion specified here, everything will be hunky-dory!

Search engine crawlers have a miserable cache hitrate

I’m looking to migrate some load off my main webserver/database, so I was looking into which of our pages render the slowest. While I was doing that, I discovered that most of our rendering time is due to just a few client IP addresses, and they turned out to be search indexers. If I group all requests by user agent (“robots”, which is only googlebot and bingbot, and “humans”, which is everybody else), I get:

Robot reqs:8062 total_sz:85MB avg_sz:10kB avg_upstr_time: 1925ms total_upstr_time: 15521s cache_hitrate: 51.3%
Human reqs:414898 total_sz:5132MB avg_sz:12kB avg_upstr_time: 32ms total_upstr_time: 13520s cache_hitrate: 98.7%

So the average robot request is some 60 times slower to render than the average human one. This is because they spend most of their time loading old pages that nobody else cares about, which are never in cache and incur heavy disk IO times from our database.

I plan to create a readonly database replica and second webserver which will be dedicated to handling requests from these search crawlers. That will stop the caches on our primary server from being wasted on old content that no humans want to see.

Installing Ubuntu Raring’s ImageMagick 6.7.7-10 on Precise

Ubuntu Precise’s package for ImageMagick is currently at version 6.6.9.7. In my PHP application, I take a transparent PNG, scale it down, then write it back out. I found that this version had a bug that caused the transparent edges of the PNG to get a dirty black background applied to them, and this problem was fixed by the time Ubuntu Raring’s version 6.7.7.10 of ImageMagick was released. So this post is about how to install Raring’s ImageMagick package into Precise.

Start by installing build pre-requisites:

sudo apt-get update
sudo apt-get install build-essential fftw3-dev liblcms2-dev liblzma-dev fakeroot perlmagick
sudo apt-get build-dep imagemagick

Download the sourcecode for ImageMagick from Raring by using the download links on this page

wget https://launchpad.net/ubuntu/raring/+source/imagemagick/8:6.7.7.10-5ubuntu2.1/+files/imagemagick_6.7.7.10.orig.tar.bz2
wget https://launchpad.net/ubuntu/raring/+source/imagemagick/8:6.7.7.10-5ubuntu2.1/+files/imagemagick_6.7.7.10-5ubuntu2.1.debian.tar.bz2
wget https://launchpad.net/ubuntu/raring/+source/imagemagick/8:6.7.7.10-5ubuntu2.1/+files/imagemagick_6.7.7.10-5ubuntu2.1.dsc

Now use dpkg-source to unpack that sourcecode for you and apply the patches:

dpkg-source -x imagemagick*.dsc

Enter that unpacked directory:

cd imagemagick-6.7.*

Edit debian/rules in your favourite text editor, find the build-stamp section and add parameters to the command-line for “./configure” that change the quantum to Q8 (meaning that ImageMagick will use the faster 8-bit pipeline internally instead of the slow Q16 one) and disable TIFF support. TIFF support requires libtiff5 which I couldn’t be bothered porting to Precise:

MagickDocumentPath="/usr/share/doc/imagemagick" ./configure --with-quantum-depth=8 --without-tiff \

Edit the install scripts to replace references to Q16 modules to Q8:

sed -i 's/Q16/Q8/' debian/libmagickcore5.install
sed -i 's/Q16/Q8/' debian/libmagickcore5-extra.install

Remove the dependency upon libtiff5-dev:

sed -i 's/libtiff5-dev//' debian/control

Disable running the test-suite (which takes forever):

export DEB_BUILD_OPTIONS=nocheck

Now, from the imagemagick-6.7.7.10 folder, build the package. The options mean don’t clean the source before build, the source is unsigned, changes are unsigned, and don’t build source packages (just binary packages):

dpkg-buildpackage -rfakeroot -nc -us -uc -b

Now you should have a full set of .deb files for ImageMagick in the parent directory! Change into the parent directory and install those:

cd ..
sudo dpkg -i *.deb

Since I wanted to be able to use ImageMagick from PHP, I also needed to install the newer version of php5-imagick to go along with it. Similar process:

sudo apt-get install cdbs
sudo apt-get build-dep php5-imagick

wget http://archive.ubuntu.com/ubuntu/pool/universe/p/php-imagick/php-imagick_3.1.0~rc1-1build2.dsc
wget http://archive.ubuntu.com/ubuntu/pool/universe/p/php-imagick/php-imagick_3.1.0~rc1.orig.tar.gz
wget http://archive.ubuntu.com/ubuntu/pool/universe/p/php-imagick/php-imagick_3.1.0~rc1-1build2.debian.tar.gz

dpkg-source -x php-imagick_3.1.*.dsc
cd php-imagick-3.1.*

dpkg-buildpackage -rfakeroot -nc -uc -b
cd ../
sudo dpkg -i php5-imagick*.deb

Then I restarted Apache so PHP could reload and pick up the new extension:

sudo service apache2 restart

And finally, according to PHP’s phpinfo(), I had the newer version of ImageMagick running!

Screen Shot 2013-11-27 at 10.07.26 pm

My macro shooting rig

I thought I would do a little write-up on the equipment I’m shooting with for macro, since my rig is pretty unusual. I’m using a lens built for old Pentax M42-mount film cameras, along with a double cable release that allows the lens’ aperture to be closed down to my shooting aperture, and the camera’s shutter to be triggered, with one smooth motion.

My macro setup

Read on for details of these components! Continue reading My macro shooting rig

Carl Zeiss Jena Sonnar 135mm f/3.5 test on full-frame

This is a nice lens for 35mm cameras, with a built-in hood. The version I tested was M42 (Pentax screw) mount.

Briefly:

  • Vignetting is only an issue wide open, improves a lot at f/5.6 and is basically gone by f/8
  • The center of the frame is already sharp at f/3.5, and only improves a little bit at f/5
  • The corners are pretty good at f/5.6 and sharpest at f/8

Please read the full review with sample images here.