Data Robotics, maker of the Drobo storage products has rolled out a nice looking high-end product that is essentially a double-wide Drobo, taking on up to 8 SATA drives:

Images courtesy of Drobo

The Drobo Pro has 8 drive bays and 3 ways of connecting to a host system: iSCSI, Firewire 800, USB 2.0.

With up to 8 drives, the Drobo now supports double-parity to survive the outright failure of 2 drives. With typical ZFS RAIDZ2 you'd need at least 5 drives (3 data + 2 parity) to support double-parity, so I'm going to assume you'd need at least 5 drives in the Drobo Pro as well for double-parity. Although technically they could default to mirroring, if you only had 4 drives, but that would cut usable space by half.

The Drobo Pro even comes with a rack-mount kit, although looks a little goofy with the 2 "wings". Seems like they could just fill it out to 12 drives across and make use of the dead space. Also, they don't list the depth of the unit, but I imagine it's relatively short compared to most rack-mount gear.

Avoid Prompts for the Admin Password when Writing to ZFS volumes

When you're creating zpools and ZFS volumes you have to be doing it with root privileges, so naturally any volume you create is going to be owned by root. So if you are trying to write to these volumes as your normal Mac login, it's going to prompt for the admin password every time.

The easy fix is just to make yourself the owner of that volume:

# chown -R UserName:GroupName /Volumes/myzpool

If you have multiple users, then use chmod to allow access to other users.

Mac ZFS Kernel Panic Crashing

First up is the more egregious behavior that I've seen so far with Mac ZFS. As I've been experimenting, I've noticed that it fails in the most ungraceful way possible (kernel panic and immediate Grey Screen of Death) when any of these conditions occur:

• You're using an external USB/FW drive for ZFS and you unplug the drive before you unmount any ZFS volumes and "zfs export -f poolname" the ZFS pool on that external drive.
• If a vdev/drive in a zpool has a failure that will put you into a FAULTED state. So on a RAIDZ (single-parity) if you lose 2 drives, that causes the kernel panic. Or on a RAIDZ2 (double-parity), if you lose 3 drives, same deal. Or in a 2-way mirror if you lose both halves of the mirror.
• Drive went to sleep or got spun down (like on a laptop or if you have the spin-down set in your Energy Saver settings).

Apparently ZFS panics (literally!) when there are an asynchronous writes that already returned "success" and would make disk state inconsistent. The supposed reason for defaulting to panics is "maintaining data integrity" because "ZFS cannot guarantee that the information in the cache, ZIL, and media will be consistent." [original post].

I don't pretend to have the best backup regime yet, but I didn't even regularly do backups until around 2004. My main system at the time was a PowerMac G3 (Blue/white). I was obliviously going day-to-day with all my primary storage on a single 80GB Maxtor drive (back when it would all fit on such a small drive).

Then suddenly one day the drive started to emit a horrible clicking sound (the dreaded Click of Death). After some attempts to scrub the drive with the lowly Disk Utility (Mac OS's fsck), the drive finally stopped mounting at all. I even tried Disk Warrior but it couldn't do anything with the drive because it wouldn't even mount. In hindsight it wasn't smart to keep doing this, as potentially there was some debris loose in the case that was ripping up the platters. At first sign of trouble, I should have stopping forcing it.

Desperation time. Searches on the Internet yielded various suggestions. One method that seemed to keep cropping up seemed a little strange, but there was enough anecdotal testimonials about it to make it worth trying. After all, the drive couldn't get much deader.

If this attempt was a bust, then worst case would be to either shell out big bucks to a drive recovery service, or just lose the data. Suddenly the cost of NOT doing regular backups came back to bite me. Pay a few hundred up front and be safe, or pay perhaps much more later on and not even be assured of getting all your data back.

Anyway, the last-ditch method I read about was the semi well-known "freezer" trick.

Data Overflow

There is never enough storage. I'm sure when computer punch cards were all the rage, you would have to constantly add more storage cabinets to hold all the cards that you collected with those way-cool math programs that would print out pi to 500 places. Then it was mag-tape reels, floppies (8-inch, 5.25-inch, 3.5-inch), optical media (CD/DVDs), and the brief popularity of the removable storage formats (remember SyQuestZip/Jaz drives? I still have some, in case I need to ummmm, boot System 7 on my Mac Quadra).

Your computer, when you bought it, came with a "massive" 80gb hard drive, then you bumped it to 320gb a couple years later. Then maybe you bumped it again to 750gb. Then you started tacking on one or two external drives to handle backups or maybe your iTunes files overflow. Now we have hard drives coming out of our ears, with 2TB drives coming on the market. Now we run out of drive bays in the computer, or have a rats nest of external hard drives and their cables strewn everywhere.

The stacks of older smaller hard drives start to pile up, and are almost like floppies now. And why not? There's no point trying to keep enough drive enclosures around, even if you get some monster 12-drive chassis.