Causing ZFS corruption for fun, NetBSD Assembly Programming Tutorial, The IKEA Lack Rack for Servers, a new OmniOS Community Edition LTS has been published, List Block Devices on FreeBSD lsblk(8) Style, Project Trident 19.10 available, and more.
Headlines
Causing ZFS corruption for fun and profit (https://datto.engineering/post/causing-zfs-corruption)
Datto backs up data, a lot of it. At the time of writing Datto has over 500 PB of data stored on ZFS. This count includes both backup appliances that are sent to customer sites, as well as cloud storage servers that are used for secondary and tertiary backup of those appliances. At this scale drive swaps are a daily occurrence, and data corruption is inevitable. How we handle this corruption when it happens determines whether we truly lose data, or successfully restore from secondary backup. In this post we'll be showing you how at Datto we intentionally cause corruption in our testing environments, to ensure we're building software that can properly handle these scenarios.
Causing Corruption
Since this is a mirror setup, a naive solution to cause corruption would be to randomly dd the same sectors of both /dev/sdb and /dev/sdc. This works, but is equally likely to just overwrite random unused space, or take down the zpool entirely. What we really want is to corrupt a specific snapshot, or even a specific file in that snapshot, to simulate a more realistic minor corruption event. Luckily we have a tool called zdb that lets us view some low level information about datasets.
Conclusion
At the 500 PB scale, it's not a matter of if data corruption will happen but when. Intentionally causing corruption is one of the strategies we use to ensure we're building software that can handle these rare (but inevitable) events.
To others out there using ZFS: I'm curious to hear how you've solved this problem. We did quite a bit of experimentation with zinject before going with this more brute force method. So I'd be especially interested if you've had luck simply simulating corruption with zinject.
NetBSD Assembly Programming Tutorial (https://polprog.net/blog/netbsdasmprog/)
A sparc64 version is also being prepared and will be added when done
This post describes how to write a simple hello world program in pure assembly on NetBSD/amd64. We will not use (nor link against) libc, nor use gcc to compile it. I will be using GNU as (gas), and therefore the AT&T syntax instead of Intel.
Why assembly?
Why not? Because it's fun to program in assembly directly. Contrary to a popular belief assembly programs aren't always faster than what optimizing compilers produce. Nevertheless it's good to be able to read assembly, especially when debugging C programs
Due to the nature of the guide, visit the site for the complete breakdown
News Roundup
The IKEA Lack Rack for Servers (https://wiki.eth0.nl/index.php/LackRack)
The LackRack
First occurrence on eth0:2010 Winterlan, the LackRack is the ultimate, low-cost, high shininess solution for your modular datacenter-in-the-living-room. Featuring the LACK (side table) from Ikea, the LackRack is an easy-to-implement, exact-fit datacenter building block. It's a little known fact that we have seen Google engineers tinker with Lack tables since way back in 2009.
The LackRack will certainly make its appearance again this summer at eth0:2010 Summer.
Summary
When temporarily not in use, multiple LackRacks can be stacked in a space-efficient way without disassembly, unlike competing 19" server racks.
The LackRack was first seen on eth0:2010 Winterlan in the no-shoe Lounge area. Its low-cost and perfect fit are great for mounting up to 8 U of 19" hardware, such as switches (see below), or perhaps other 19" gear. It's very easy to assemble, and thanks to the design, they are stable enough to hold (for example) 19" switches and you can put your bottle of Club-Mate on top! Multi-shiny LackRack can also be painted to your specific preferences and the airflow is unprecedented!
Ho