Archive for September 2011
A few weeks ago, the company I work for had some issues with a server used to host a central file repository. It was nothing more than a windows server with a lump of drive space shared out, and a mapped drive on all of the user workstations. Backups were made using a backup appliance (managed by a vendor) that would take incremental snapshots of every file, and store the last X revisions until the device ran out of space. At that point it would start to overwrite the oldest files. As a secondary measure, full snapshots of the data were taken every X days, to guard against a double failure of the drive and the backup appliance.
Unfortunately, because of a known (unknown to us..) issue with a software package that was installed on the server, the master file table was being corrupted. Because the files were ‘changed’, the backup device would copy over the corrupted files, overwriting the backups. I’m sure you can see where things went from there..
Forutnately, once we realized what was happening, we were able to piece together %95 of the data that was lost. The remaining data consisted of files changed/created since the last full snapshot. I found myself in a position of having to sort through literally hundreds of thousands of files trying to find the most-recent, working copy of each particular file. Not impossible, but impossibly inefficient. I came across a tool called Beyond Compare. It allows you to compare two directory structures, and shows you any files or folders that are different between the two directories. You can tell it what criteria it should use to determine if files are the same, and it highlights the entire directory structure up to the top level if there are any differences, with different colors for different discrepancies. You can even open two files side-by-side to decide exactly which version you want to keep. At that point, you are a click away from correcting the problem. I would probably still be working on this if I had not found this tool.
So now we are back in business with a working copy of the drive. But what was to keep this from happening again? After all, we shouldn’t have used ignorance as an excuse once, and we definitely couldn’t use it twice. I started thinking about file systems, and I realized that there really was no good protection for this sort of failure, other than to have a file system that builds some sort of CRC or hash into the files / directory structure itself. I wondered if such a thing existed, and thats when I found out about ZFS.
ZFS stands for Zettabyte File System. If you’re not familiar, look it up because it has some interesting features. In my situation, I was mostly interested in it’s data integrity features. I won’t go into full detail here, but it fully covers our modest needs. The question was, what is the easiest way to build a windows share on a file system that windows doesn’t support?
That’s when I came across FreeNas. It’s an open-source NAS appliance in the form of a live-CD image. It runs acceptably on almost any hardware I threw at it. It’s extremely easy to use, it uses ZFS for storage, it’s relatively stable and mature, and best of all, it’s free.
Check it out!
I’ve had this little guy for about 2 months now, and every day I find myself in a situation in which I need a pocket-sized flashlight. I originally purchased this guy for around $11 (shipped!), and I can’t say I had very high expectations at that price!
My expectations were wrong in almost every way. I’m very impressed with the build quality. It’s very compact; it takes a single AA or 14500 lithium and is not a whole lot bigger than the battery itself. That does not mean that it’s fragile, mind you. The machined aluminium housing is almost 3 mm thick in places, and I’m fairly certain that I could run this thing over with a small truck without damaging anything. The machining is more than adequate; it threads together nicely with no tight spots. Everything fits and works the way it should. It is sealed with O-rings at both ends, and I can confirm that it is waterproof to at least a few feet, if not much further.
I haven’t found the holster to be very useful, mainly because I threw it out when I first got it. The quality was fine; I’m just not a fan of carrying things on a belt. It also comes with one of those wrist straps that narrow down to a micro-thread to attach to the flashlight itself. Typically I remove them because they tend to get tangled in tool bags / pockets, but I left this one on, and it is pretty tough.
Electrically, it has a single-mode (on/off) electronic regulator that draws about 850 milliamps when used with a single 3.6v, 900mah lithium ion cell (type 14500), which works out to a little over 1 hour of runtime between charges. I actually prefer single-mode regulators on a flashlight of this size. I’ve never found myself in a situation where it was just too bright. The wide shoulder of the light pattern gives you a good amount of control over just how much illumination your subject receives.
Light output is great for it’s size; I believe it’s rated at ~190 lumens, which means it certainly isn’t the brightest flashlight on the market. Light pattern is a very subjective matter, however I will say that it has proven to be very functional in my real world usage. It has an average flood beam that covers a large area at distances of 2-3 feet, combined with a central spot that usable up to around 55 feet at night. As far as intensity, I recently used this flashlight to gain the attention of a co-worker situated inside a building, 2 stories above me by shining the light through their window. The central spot is very visible, even in broad daylight.
As you can see, I’ve lost some of the anodized finish. I usually carry around a full-on high-school-janitor sized ring of keys alongside this flashlight, so a little damage is to be expected. It’s actually quite tough considering the circumstances.
Hello and welcome to my blog. My goal is to share my experiences with the various products that I come into contact with, both at home and in my carreer. The title is DiyGadgetReview, however I hope to share more than just gadget reviews. Tips, techniques, and plain-old best practies are among the topics that I will be covering. I encourage comments as well as feedback, however your comments should be kept clean and be relevant to the original subject of the post.
Thanks for tuning in!