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Category: Computer Science

Backblazing…

So there is Backblaze B2. It’s a service where you can buy bulk disk space online for backup and restore.

I have a Linux server at home, which many harddisks and which downloads and saves all data from the various dedicated servers and cloud instances, receives several time machine backups from the inhouse Apples, and has local git repositories and stuff.

I mirror these things from the production filesystems to a set of mostly offline disks once, and I wanted an off-site backup as well for crash recovery. Bandwidth is not a problem, we are living on FTTH with 500/500.

So there is rclone for this. It’s like rsync for B2 or other services.

Like so:

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How to Debug “My Mac won’t go to sleep”

In Terminal,

pmset -g assertions

The pmset program debugs power management. Assertions describe the system state as perceived by power management and if and when the system can go to sleep.

Example output:

$ pmset -g assertions
2017-11-02 16:31:14 +0100
Assertion status system-wide:
BackgroundTask 0
ApplePushServiceTask 0
UserIsActive 1
PreventUserIdleDisplaySleep 1
PreventSystemSleep 0
ExternalMedia 0
PreventUserIdleSystemSleep 1
NetworkClientActive 0
Listed by owning process:
pid 1310(Google Chrome): [0x00012f7c00018f49] 00:00:40 NoIdleSleepAssertion named: "Playing audio"
pid 1310(Google Chrome): [0x00012f7c00058f48] 00:00:40 NoDisplaySleepAssertion named: "Playing video"
pid 241(coreaudiod): [0x00012f7c0001810f] 00:00:40 PreventUserIdleSystemSleep named: "com.apple.audio.AppleHDAEngineOutput:1B,0,1,1:0.context.preventuseridlesleep"
Created for PID: 1310.
pid 113(hidd): [0x0000957f0009876f] 49:51:56 UserIsActive named: "com.apple.iohideventsystem.queue.tickle.4294975161.3"
Timeout will fire in 10796 secs Action=TimeoutActionRelease
Kernel Assertions: 0x10c=USB,BT-HID,MAGICWAKE
[...]

UserIsActive, because I type right now.

PreventUserIdleDisplaySleep because coreaudiod (pid 241) has been asked by Chrome (pid 1310) to do this. So the screen won’t blank because Chrome is doing a video playback.

PreventSystemSleep is 0, so the system will sleep when I close the lid.

If you have for example Internet Sharing or Screen Sharing enabled, you can see PreventSystemSleep here:

pid 77674(screensharingd): [0x000155590007906d] 06:30:03 PreventSystemSleep named: "Remote user is connected"

This will also set PreventSystemSleep to 1 in the overview list “Assertion status system-wide”.

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What GPUs can do…

Pcgamer reports “Nvidia CEO says Moore’s Law is dead and GPUs will replace CPUs“. Now, Jensen Huang might be a bit biased here, but he reminded us that “GPUs are advancing at a much faster pace than CPUs” and “that GPUs will replace CPUs soon, adding that at this point, designers can hardly work out advanced parallel instruction architectures for CPUs.”

So what can a modern GPU do? Well, apparently Font Rendering is still a hard problem for GPUs, and a bottleneck in modern browsers. That’s not to say it’s not being done – the linked article contains lot of pointers.

And an older article about the Ubershaders basically explains how the Dolphin GameCube/Wii-Emulator uses modern GPU hardware to live-emulate 2002/2006 GPU hardware, in realtime (for a short time, while the CPU in the background creates more optimised precompiled GPU setups and code).

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The missing standard for Datacenter Space…

20th century dross

There is a very nice talk by John Laban on the accumulation of cruft and old style features in how we are currently building data centers. Being an advocate for the Open Compute Foundation, Laban is an advocate for OCP, which at the core has several ideas.

One of them being the vision of a Data Center Room, Rack and Machine as a system that are depending on each other in construction.

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The Great DOM Fuzz-off of 2017

I generally recommend people use a current stable Chrome. It’s the most secure browser. Please also install uBO and use 1Password.

Turns out, that recommendation can also be backed up by data. Check the “Results” headline.

Note also how they did not test Safari on Apple, because that hurts too much:

Instead of fuzzing Safari directly, which would require Apple hardware, we instead used WebKitGTK+ which we could run on internal (Linux-based) infrastructure. We created an ASAN build of the release version of WebKitGTK+. Additionally, each crash was verified against a nightly ASAN WebKit build running on a Mac.

Yup, Apple development and testing happening on Linux.

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How The Internet Kept Humming During 2 Hurricanes

The New York Times has a nice article about Data Center Infrastructure vs. Hurricanes, suitable for muggles.

Yet another data center, west of Houston, was so well prepared for the storm — with backup generators, bunks and showers — that employees’ displaced family members took up residence and United States marshals used it as a headquarters until the weather passed.

“It wasn’t Noah’s ark, but it was darn close,” said Rob Morris, managing partner and co-founder of Skybox, the company that runs the center.

 

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