The agony has gone on long enough: from an idea in 2006, to a proof of concept in mid-2007, a business plan and a hopes of a start-up (under the name of Tucana, d.o.o.) in 2008, directly to the dustbin of history.
I’ve just pulled the plug and shut it down.
Its ideas were good: a wikipedia-inspired revision based subtitling and subtitle translation service, which would help spread the knowledge in the form of flash-based videoclips. It’s been obsoleted by other projects with more traction, such as DotSub and TED translations (incidentally, most of the clips I was inspired by and wanted to share with people, whose first language was not English, came from the TED itself). Now that Youtube’s language recognition and Google’s machine translation have gotten much better, there’s less and less need for painstaking transcription and all the manual work.
If I had to choose one thing to blame for its lack of success, underestimating the difficulty of transcribing video would be it. It literally takes hours to accurately transcribe a single clip, which is no longer than a couple of minutes.
I’ve tried rebranding and repurposing it into a Funny clip subtitler and at least got some fun and local enthusiasm out of that. However, it’s all a part of one big package which now needs closure.
Some ideas I’ve had were never implemented, although I thought they had great potential; I wanted to bring together large databases of existing movie and TV show subtitles with the publicly available video content in Flash Video. Since at the time almost all video on the web was FLV, there was no technological barrier. And there’s still a lot of popular TV shows, movies, etc, burried deeply in the video CDNs (Youtube, Megavideo, Megaupload), and large databases of “pointers” are maintained and curated by different communities (Surfthechannel.com, Icefilms.info). Having the video and the subtitle available instantly, without the cost of hosting large files, was a textbook Mash-up idea.
I’m posting some screenshots below, for the future me, so I can remember what I was spending countless hours of my time on. Yes, the design’s ugly, but bear in mind it was all a work of one man, eager to add functionality, and pressed into kickstarting the content generation by also transcribing and translating a bunch of videos.
Thanks to all who shared the enthusiasm and helped in any way.
So far I’ve been pretty satisfied with my Nexenta setup. Dedup is a great feature and I’ve rsynced all other computers to it without a single thought of which files are copied more than once (all Windows and program files, multiple copies of pictures, multiple copies of Dropbox dirs, etc.). However, the following three things drove me nuts; here’s a word on how I’ve resolved them.
Smbshare vs. Samba
Yes, native ZFS smbshare is great; it even exposes snapshots as “Previous versions” to Windows boxes. And it can be simply managed from napp-it. However, smbshare won’t allow you to share the file system’s children
Here’s how this works: let’s say you have 3 nested file systems:
mypool/data
mypool/data/pictures
mypool/data/pictures/vacation
When you share mypool/data and navigate to it, you won’t see the pictures dir. When you navigate to pictures, you won’t see the vacation dir.
It drove me crazy and it seems it won’t be supported anywhere in the near future. That’s why I disabled smbshare completely and installed plain old Samba. Because Samba’s not ZFS-aware (but instead a plain old app that accesses the file system) it shares everything as you’d expect. Problem solved.
Backing up an entire zpool
I wanted the following:
to backup the entire data pool to an external USB drive of the same capacity (2TB)
a solution that would be smart enough to recognize matching snapshots and only copy the diffs
it should also delete the destination snaps that no longer exist in the source pool
it wouldn’t hurt if it supported remote replication in case I wanted that later
Much has been written about the awesomeness of zfs send | zfs receive, but I was immediately disappointed by all the manual work that still needed to be done. Sure, it supports recursive send/receive, it can be used over ssh, but it only operates on snapshots. It can incrementally copy the last delta (if you tell it exactly which two snapshots are to be used for diff), but if you prune your old snapshots to save space, it won’t know anything about that. So your backup size will grow indefinitely, constantly appending more data.
What I wanted was a simple 1:1 copy of my pool to an external drive. I even considered adding the drive to the mirror to create a 3-way mirrored pool; once resilvering would complete, I could split the mirror and disconnect the USB drive. However, resilvering is not that smart and takes days; all the data needs to be copied every time, and making a snapshot interrupts and restarts the process.
Then I found the excellent zxfer. It does work on Nexenta and allows you to mirror an entire pool; the procedure is pretty straightforward: first determine the path of your external USB drive using rmformat:
#rmformat
1. …
2. Logical Node: /dev/rdsk/c3t0d0p0
Physical Node: /pci@0,0/pci103c,1609@12,2/storage@3/disk@0,0
Connected Device: WD 20EADS External 1.75
Device Type: Removable
Bus: USB
Size: 1907.7 GB
Label: <Unknown>
Access permissions: Medium is not write protected.
On subsequent runs it identifies the last common snapshot and copies only the diffs. [-d] switch deletes pruned snapshots from the target pool. For more, read the zxfer man page.
Virtualbox
This has been pretty disappointing; it’s a pain to set it up and it performs badly (that is, compared to VmWare on similar hardware). It burns around 15% of the CPU running an idle and freshly installed Ubuntu box. Command-line config is a pain and virtualizing (P2V) certain Windows boxes spits out errors that (according to Google) noone has ever seen before. The same image Just Works ™ under VmWare.
Nonetheless, it’ll have to do for now. For more info on how to set it up, consult the following:
I wanted this because the 7200 RPM disk that shipped with HP Microserver makes an annoying metallic noise when spinning. USB key is quieter, greener and frees an additional disk bay. Also, Microserver has an extra USB slot inside the chasis just for this purpose.
However, the operation was not as simple as I thought1 — because you can’t shrink zpools (that is, shrink from the 250GB internal drive to the 16GB USB drive).
So I had two options: reinstall from scratch and choose USB stick as the target, or move the existing system. I chose the latter to avoid the reconfiguration. However, if you haven’t installed it yet and are thinking about this as a future upgrade path, I recommend you skip the HDD entirely and go directly to USB stick; it will save you a lot of trouble.
In the end, this process worked:
Install Nexenta (fresh install) on USB key (I did this using VMWare and USB passthrough). This creates suitable partition table, installs grub and saves many other steps as well.
Boot the old system (disable usb boot) and plug in the USB stick.
Import new zpool on the usb stick as newsyspool (to distinguish from old syspool).
Delete all filesystems in newsyspool using zfs destroy newsyspool/dump (also: newsyspool/swap, newsyspool/nmu… everything); this deletes all data on the USB drive — we just need partitions (i.e., ZFS slices).
Make a snapshot of the old (internal HDD) syspool: zfs snapshot syspool@20111112
Copy entire internal HDD (i.e., syspool) to the USB stick: zfs send -R syspool@20111112 | zfs recv -vFd newsyspool
Set boot property of the USB drive in the same way than that of your internal HDD. Get the latter with zpool get bootfs syspool (this shows old bootfs property, e.g., syspool/rootfs-nmu-000). Then set the former (newsyspool on USB drive) with zpool set bootfs=newsyspool/rootfs-nmu-000 newsyspool
Set noatime=off to disable writing a timestamp on every read: zfs set noatime=off newsyspool
Disconnect your internal HDD, set bios to boot from USB drive and reboot.
If the system doesn’t boot, just reconnect the old drive and you haven’t lost anything.
If the system boots, delete the old syspool which is now faulted (since there’s no HDD): zpool destroy syspool (warning, this asks for no confirmation! be sure you’ve booted from USB!)
About 1 month after the upgrade the USB key failed; the server wouldn’t boot (stuck at grub loading stage2), so I plugged back the old HDD, scrubbed USB key zpool and it found approx. 1000 errors, of which 500 were unrecoverable. It was not the cheapest USB key (PQI), but the constant swapping or whatever Nexenta’s doing when nobody’s looking must have killed it.
What I thought was this: plug in the USB stick, create a mirrored syspool and remove the HDD [↩]
I’ve written about my small and green home server before. I love its low power consumption, integrated UPS/keyboard/screen and the small size.
But it was time for an upgrade — to a real server.
Size comparison: HP Microserver vs. Asus EEE
The reasons for an upgrade
The thing I missed most was more CPU power. The 600 MHz Celeron CPU got pretty bogged down during writes due to NTFS compression. With more and more concurrent writes, the write performance slowed down to a crawl.
Then there was a shortage of RAM. 1 GB is enough for a single OS, but I’m kind of used to virtualizing stuff. I wanted to run some VMs.
Also, I’ve been reading a lot about data integrity. This was supposed to be my all-in-one central data repository, but was based on cheap hardware with almost no data protection at all:
My single drive could easily fail; it would be nice to have two in a mirror (also, not USB).
Bits can randomly and silently flip without leaving any detectable signs (the infamous bit rot).
Memory corruption does happen (failing memory modules) and more, bits in RAM flip significantly more often (memory bit rot or soft errors) than on hard drives.
So what I wanted to combat these problems was:
a server that’s still as small, as silent and as green as possible;
has a more decent CPU and plenty of RAM;
supports ECC RAM (stands for error correcting);
and can accomodate an OS with native ZFS file system.
Why worry about data integrity all of a sudden?
Well, they say the problem’s always been there: bit error rate of disk drives has been almost constant since the dawn of time. On the other hand, disk capacity doubles every 12-18 months.
This loosely translates to: there’s an unnoticed disk error every 10-20TB. Ten years ago one was unlikely to reach that number, but today you only need to copy your 3TB Mybook three times and you’re likely to have some unnnoticed data corruption somewhere. And in 5-7 years you’ll own a cheap 100TB drive full of data.
Most of today’s file systems were designed somewhere in the 1980s or early 1990s at best, when we stored our data on 1.44MB floppies and had no idea what a terabyte is. They continue to work, patched1 beyond recognition, but they were not really designed for today’s, let alone tomorrow’s disk sizes and payloads.
Enter ZFS
ZFS is hands down the most advanced file system in the world. Add to that some other superlatives: the most future proof, enterprise-grade and totally open-source. Its features put any other FS to shame2:
it includes a LVM (no more partitions, but storage pools),
ensures data integrity by checksumming every block of data, not just metadata,
automatically corrects data (for this, you need 2 copies of it — that’s why you need a mirror or copies=N setting with N>1)
compresses data (with up to gzip-9), which is extremely useful for archival purposes and also speeds up reads
can send filesystems or their deltas to another ZFS or to a file, and re-apply them back,
can seamlessly utilize hybrid storage model (cache most used data in RAM, and a little less used data on SSD), which means it’s blazingly fast3,
integrates iSCSI, SMB (in the FS itself), supports quotas, and more.
Of course ZFS can use as much ram as possible for cache, plus about 1GB per 1TB of data for storing deduplication hashes. And since the integrity of data is ensured on the drive, it would be a shame for it to get corrupted in RAM (hence, ECC RAM is a must).
The setup
Getting all this packed inside a single box looked like an impossible goal — until I found the HP Proliant Misroserver. You can check the review that finally convinced me below.
The specs are not stellar, but it provides quite a bang for the buck4.
It’s a nice and small tower of 27 x 26 x 21 cm with 4 externally accessible drive bays and ECC RAM support;
CPU is arguably its weakest point: Dual-core AMD N36L (2x 1.3 GHz); however, the obvious advantage of AMD over Atoms is ECC support;
It includes a 250GB drive and 1GB ram, but I’ve upgraded that.
upgrade 1: 2x 4GB of ECC ram; as I said, ECC is a must for a server, where a bit flip in memory can wreak havoc in a file system that is basically a sky-high stack of compressed and deduplicated snapshots.
upgrade 2: 2x 2TB WD green; it’s energy efficient and can be reprogrammed to avoid aggressive spin-downs.
All together, the server loaded with 3 drives consumes only 45W. It’s not silent, but it’s pretty quiet.
Here’s a quick rundown of what I’ve done with it, mostly following this excellent tutorial (but avoiding the potentially dangerous 4k sector optimization):
I installed Nexenta Core, which is a distro combining Solaris kernel with Ubuntu userland. I’ve read many good things about it and find it more intuitive and lean than Solaris.
Note: as Nexenta currently doesn’t support booting from a USB key, I had to use an external CD drive, which I hacked from a normal CD drive and an IDE-to-USB cable.
I reconfigured WD Green HDDs to disable frequent spindowns.
But: I avoided fiddling with the zpool binary from the tutorial above because it can cause compatibility issues and data loss and brings little improvement.
I finally added the excellent napp-it web GUI for basic web management. This comes pretty close to a home NAS appliance with the geek factor turned up to 11. You can monitor and control pretty much everything you wish (see below for a screenshot).
Napp-it web GUI -- pool statistics
I configured two drives as a mirrored pool and created a bunch of filesystems in it. A ZFS filesystem is quite analogous to a regular directory and you can have as many filesystems (even nested ones) as you wish. Each separate ZFS can have individual compression, deduplication, sharing and mount point settings (however, deduplication itself is pool-wide).
Just for feeling, the deduplication and compression at work: with about 630GB of data currently on it (of which there’s about 500GB of Vmware backup images of three servers), the actual space occupied is 131 GB.
urban@titan:~$ zpool list
NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT
syspool 232G 6.96G 225G 2% 1.00x ONLINE -
tank 1.81T 131G 1.68T 7% 2.13x ONLINE -
If we look at zpool debugger stats about compression and deduplication, we see there’s a lot of both going on:
urban@titan:~$ sudo zdb -D tank
DDT-sha256-zap-duplicate: 695216 entries, size 304 on disk, 161 in core
DDT-sha256-zap-unique: 1122849 entries, size 337 on disk, 208 in core
dedup = 2.13, compress = 2.04, copies = 1.00, dedup * compress / copies = 4.35
From here on
So far I’ve been more than satisfied. I’ve written about deduplication before, and this here is by far the most elegant and robust solution. Of course there’s a bunch of stuff to do next.
The first one is virtualization, and here my only option (this being a Solaris kernel) is Virtualbox. Until now I’ve sworn by Vmware, but image conversion is actually pretty straightforward (using the qemu-img tool).
The first candidate for virtualization will be my old EEE, because I still need Windows for running a couple of Windows-only services. The virtual EEE should also be able to mount the ZFS below, either via SMB or iSCSI (Microsoft does provide free iSCSI initiator which I’ve successfully used before), which should ensure smooth transition to the new server.
One of the things that bothers me in Mac OS X is that you cannot delete files without skipping the trash (apart from using the console). This means that to free the disk space of, say, a 2GB file, you have to empty the trash; if you delete large files often, your trash either grows very large or you empty it so often, that it defeats the very purpose of having one.
Until now I’ve used a handy script/droplet Permanently shred, but it broke in Lion. So here’s how you make your own “Skip Trash” dock app using Automator.
1. Start Automator
2. Choose “Application”
3. Search for “Ask for confirmation” and drag it to the right pane
4. Enter a confirmation message, e.g. “Are you sure?”
5. Search for “Run shell script” and drag it to the right pane
6. Select “Pass input: as arguments”
7. Replace “echo” with “rm -rf”
8. Save application (e.g. as SkipTrash.app)
9. drag it to the dock and select “Options -> keep in dock”
If you want the app to play a Poof sound when finished, add “afplay /Library/poof.aif” at the end of the shell script and unzip and copy this file to your /Library/ (or any other location you want, but update the path accordingly): poof.aif.zip
So now whenever you want to skip the trash, drop files or folders onto the newly created SkipTrash.app instead of the regular Trash icon.
Urban:
Hey, thanks for your elaborate comment.
Regarding SMB, I think Samba is a pretty decent workaround as well; as far as I can tell, all you lose is "pre
Mozaik. » Blog Archive » Subtitlr retires:
[...] agony has gone on long enough: from an idea in 2006, to a proof of concept in mid-2007, a business plan and a hopes of a start-up (under the nam
Gea:
about SMB
There are efforts to solve this problem.
Currently: Each ZFS dataset is completely independant from others. You can set a mountpoint to moun
