Interview with
John Kozubik


Cloud storage in the form of a UNIX filesystem available over SSH.


What is is a cloud storage provider focused on offsite backup. I like to think of it as a safe-deposit box for data.

What makes special is that there is no app or API - we simply give you an empty UNIX filesystem accessible with any SSH tool.

What problem does solve?

Originally - in 2005 - the problem was simply "cloud storage" and the ability to make offsite backups easy for people that didn't have their own colocation or datacenter assets.

Now, of course, there are lots of cloud storage providers - the problem we solve in 2021 is interfacing with cloud storage directly on the UNIX command line using UNIX tools and practices.

Sometimes people just want to rsync or sftp a file somewhere without installing new tools. At the same time, we now support a number of very exciting tools (like borg, restic, rclone, git-annex, etc.) that add a lot of power to the UNIX command line environment. is not built on a cloud platform - we own (and have built) all of our own platform. Our storage arrays, as we call them, are 2U "head units" with x16 2.5" drive slots and one or more SAS HBAs.

ZFS makes good use of fast cache storage so, after using up two drive slots for our boot mirror (which is always a mix of two totally different SSDs) we have room for up to 14 more SSDs for read (L2ARC) and write (SLOG) cache. ZFS is also RAM hungry so we choose a motherboard that can support up to 2TB of RAM.

Attached to these head units, externally, are one or more JBOD chassis filled with hard drives. JBOD stands for "just a bunch of disks" and they are typically 4U chassis containing 45 or 60 drives that attach back to the head unit with SAS cables. has no firewalls and no routers. In each location we connect to our IP provider with a dumb, unmanaged switch.

This might seem odd, but consider: if an storage array is a FreeBSD system running only OpenSSH, what would the firewall be ? It would be another FreeBSD system with only port 22 open. That would introduce more failure modes, fragility and complexity without gaining any security.

What does a "day in the life" look like?

I start the day with a short walk outdoors. I don't want the first thing my eyes see to be print, and I don't want the first thing my body does to be sitting. So I walk a bit.

Then I sit down and read hackernews with some coffee.

I try to maintain an "Hedonic Fast" Monday through Wednesday so, on those days, I am only looking for truly actionable headlines and comment threads that are relevant to my businesses. On other days I read (and comment) for pleasure - typically HN but also MetaFilter, Marginal Revolution, Crooked Timber, The Believer, and the excellent London Review of Books.

I spend my work day in a terminal window and a browser window. The terminal window is typically open to email which I read with Alpine and the browser window is open to our home-grown CRM/management website. I do not typically handle technical support but I do answer the "info" mailbox where pre-sales and other informational requests end up.

I usually spend about two hours with these tools before lunch - checking Key Performance Indicators (both corporate and computational) in our management system and having email conversations with potential and existing customers.

At some point in the morning I will have a phonecall with my lead engineer, Dave Boodman, and we'll have a very high bandwidth discussion about all aspects of operations. Dave then delegates the results of these conversations to everyone on our team at all of our locations.

Finally, if I am lucky and all of the housekeeping and firefighting can be taken care of, I spend the afternoon working on longer term development projects and strategic initiatives, etc.

What is the team structure around has a handful of full-time employees - most notably myself, the CEO, and my lead engineer who I have worked with, across three startups, since 1998.

In addition, we have contract employees that we regularly utilize in our different datacenter locations as well as a handful of contract coders around the world.

How did you first get into software development?

I got started in software by copying BASIC programs from magazines onto my commodore 64.

Although I have written software, sporadically, throughout my career my life's work is as a systems designer or systems engineer. If we're not using fancy titles I am really just a UNIX sysadmin.

I got started with UNIX in 1992 when my father loaded ESIX onto his 386 from 50 floppy disks. The next year I got a dial-up login to the SunOS system(s) and promptly got myself banned from irc.

At some point along the way I settled on FreeBSD as server OS of choice and have built every one of my startups entirely on that platform - including which runs solely on FreeBSD.

What is the most interesting development challenge you've faced working on

When began, in 2001, we were using UFS2 filesystems on top of hardware RAID arrays built from 80 and 120 GB hard drives. We ran this way using RAID6 arrays on 3ware controllers for many years and it was a very simple and elegant platform. In the past it has always pleased me, from the standpoint of simplicity, that the RAID controller presents a single device to the OS and the OS thinks it just has one big giant disk.

Problems began to arise as early as 2008, however, as we began to push the boundaries of UFS2 - both in terms of filesystem size and number of inodes (files). Not only did we start to see prohibitively long fsck times but we started to run out of memory address space that fsck could track inodes with.

At some point in 2011, while working with Kirk McKusick, the author of UFS, I wondered out loud what the real, long-term solution was to the problems we were having as we pushed UFS2 well beyond its design ... and he simply said "use ZFS".

So we embarked on a two year testing and development project to stress test and deploy ZFS which culminated in our first production ZFS systems in 2013. It took another four years before we migrated the final UFS2 storage array to ZFS.

This was a relatively large undertaking for us and was, in essence, a complete reworking of our cloud storage platform. It was well worth it as ZFS, as McKusick predicted, solved all of our problems. Further, it enabled new use-cases for us as the point-in-time snapshots that ZFS can create and maintain are now a critical feature for our users.

What is the most interesting tech you are playing around with at the moment?

As a hobby I have been slowly building my own personal phone company with Twilio as the back-end. I have nostalgia for telephony and phone phreaking and it pleases me greatly to send SMS messages, from my mobile number, from the command line (among other things).

In fact, I have a small suite of little shell scripts that do telephony tasks and do almost all of my texting from the UNIX command line.

Describe your computer hardware setup

I have a early-2009 "octo" Mac Pro that I bought new 12 years ago. Other than adding a USB3 card it is in its original configuration and it feels smooth and performant. Even when I load VMWare Fusion I don't notice that I am on an old machine ...

I have four monitors attached to this workstation - three of which are on my desktop in a familiar triple-monitor configuration and one of which is an NEC P461 commercial display in the next room. You've seen these monitors - they are used for arrival/departure boards in airports and they are "dumb" flat panels that last forever. It pleases me to drag a window off the edge of my desktop display and into the next room ...

Describe your computer software setup

OS: macOS. I have no data stored, locally, on my workstation - everything is on a server I keep at a datacenter so I initiate my work in the terminal by port-knocking, logging in over SSH and attaching to my GNU screen session. When I login, one of those Twilio scripts sends an SMS alert notifying me of that fact.

I believe very strongly in the superiority of tiling / non-overlapping window management and I accomplish this in macOS with Spectacle although I believe that is no longer maintained and there are better tools for that now.

I load a utility called "ykeys" that allows me to set custom hotkeys for volume and pause/unpause, etc.

I dislike interacting with my iPhone on an import/export basis and I refuse to use an mp3 player as my backup tool so I have purchased a license for Macroplant iExplorer which lets me browse the iPhone like a filesystem.

Finally, I use Rich Somerfields TextBar app to put a few, scriptable, pieces of information into my macOS menu bar. Specifically, I like to see what wireless AP (SSID) I am connected to and what IP address I appear to be browsing from. I have specific expectations about those two and I want to see, immediately, if they are different than I expect them to be.

When I bought my current workstation, 12 years ago, I felt that it was indeed a UNIX-like system. I do a lot of basic use and maintenance on the command line of macOS using commands like 'airport' and 'drutil' and 'diskutil', etc. I'm also quite happy with Homebrew for package management.

However, I can see the shell environment becoming more and more restricted as macOS continues to lock down actions and disallows even root from controlling things. I suspect I am going to need to go back to FreeBSD as a desktop environment and that should be relatively easy for a workstation that does not use wireless networking and never prints, etc.

It's going to be a lot harder to make that switch with my laptop ...

Browser: Firefox. I have exactly one extension: uBlock Origin.

Email: My email client is running on the remote system and I interact with email using Alpine in the terminal. This is very interesting because it means that when I send an email to another person at, the email never traverses any network - it is just a local copy operation because they, also, use alpine.

Chat: I used to always (as in, for 25 years) have an IRC client running in one of my screen windows but ... that platform, at least among my friends, has died off.

IDE: Inasmuch as I have an IDE it is vim with some very minor tab/folding customizations. I also use an interesting vi-related tool named 'vimv' which, if run in a directory, lets you manipulate the filenames in that directory in 'vi' as if you were editing a text file. If you have a number of hard-to-script files to rename, 'vimv' makes it easy.

Why connect remotely rather than having a local dev environment?

It's a workflow I've been using since 1999 when I put my own machine into a datacenter for the first time.

A text only workflow doesn't suffer (much) from working over a WAN link and it pleases me greatly to know that there is nothing of value on my laptop or workstation - if they were lost or stolen it would be temporarily inconvenient but not disastrous.

Describe your desk setup

The desk of John Kozubik,

I work at a standing desk that is a slab of old bowling alley. The desk is height adjustable using Linak actuators but I very seldom lower it. If I don't want to stand I will just lie on the couch with a laptop.

When coding

Daytime or nighttime? In terms of motivation and aesthetic preference I would much rather do actual development work late at night - perhaps 10pm to 2am. Historically, my best and most valuable work was done at that time.

However, I have three children and many responsibilities at home so that time slot no longer exists for me. As mentioned above, if I have time for real development it is in the afternoon after all of the housekeeping and firefighting are over.

Tea or coffee? Coffee. We have such tremendous, wonderful coffee in the bay area and I appreciate every bit of it. I especially like Equator Coffee which is based here in Marin County.

Silence or music? It depends. If I need to concentrate and think through complex issues I prefer silence. If I am doing housekeeping activities or mindless, rote work, I like to listen to music. I find the soundtrack and film scoring that Trent Reznor has done in recent years (Social Network, Girl with Dragon Tattoo, Watchmen) to be very good.

What non-tech activities do you like to do?

I am a BJJ player and have been doing that on and off for 20 years. I also have a Kung Fu / Tai Chi practice and do a lot of running and biking here in Marin County where I live. I'm also a volunteer firefighter/medic with my small town fire department.

Find out more is cloud storage in the form of a UNIX filesystem available over SSH. It was featured as an "Interesting Tool" in the Console newsletter on 28 Jan 2021. This interview was conducted on 12 Mar 2021.