A DC busbar can propagate a short circuit across the rack, and DC circuit protection is harder than AC. So of course each server now needs its own current limiter, or a cheap fuse.
But I’m not debating the merits of this engineering tradeoff - which seems fine, and pretty widely adopted - just its advertisement. The healthcare industry understands the importance of assessing clinical endpoints (like mortality) rather than surrogate measures (like lab results). Whenever we replace “legacy” with “cloud”, it’d be nice to estimate the change in TCO.
> > The power shelf distributes DC power up and down the rack via a bus bar. This eliminates the 70 total AC power supplies found in an equivalent legacy server rack within 32 servers, two top-of-rack switches, and one out-of-band switch, each with two AC power supplies
This creates a single point of failure, trading robustness for efficiency. There's nothing wrong with that, but software/ops might have to accommodate by making the opposite tradeoff. In general, the cost savings advertised by cloud infrastructure should be more holistic.
As you noted, Apple's fsync() behavior is defensible if PLP is assumed. Committing through the PLP cache isn't how these drives are meant to operate - hence the poor behavior of F_FULLSYNC.
But this isn't specific to Macs and iDevices. Some non-PLP drives also struggle with sync writes on FreeBSD [1]. Most enterprises running RDBMS mandate PLP for both performance and reliability. I understand why this is frustrating for porting Linux, but Apple is allowed to make strong assumptions about how their hardware interoperates.
The first problem is rendering within the guest. If you only have one GPU, then GVT-g [1] virtualizes it with just a bit of overhead. But it's Intel only.
The second problem is getting those pixels onto your screen in the host. SPICE is not as fast as Looking Glass [2], which sets up a shared memory buffer between the host and guest. This has acceptable performance even for modern games.
The OP doesn't seem to utilize these techniques, so I don't think it can plausibly claim to have the fastest configuration - at least not yet.
Those images are hashed, not transmitted in original format. On top of that, PSI prevents you from learning those hashes, or how many there are. So you can’t tell if the database contains the hash of, say, tank-man.jpg.
I understand why this shielding is necessary for the system to work. My point is the crypto is being used to protect law enforcement, not the user.
> recruited mathematicians to analyze it, and published the results, as well as one in-house proof and one independent proof showing the cryptographic integrity of the system.
Apple employs cryptographers, but they are not necessarily acting in your interest. Case in point: their use of private set intersection, to preserve privacy..of law enforcement, not users. Their less technical summary:
> Instead of scanning images in the cloud, the system performs on-device matching using a database of known CSAM image hashes provided by NCMEC and other child safety organizations. Apple further transforms this database into an unreadable set of hashes that is securely stored on users’ devices.
> Before an image is stored in iCloud Photos, an on-device matching process is performed for that image against the known CSAM hashes. This matching process is powered by a cryptographic technology called private set intersection..
The matching is performed on device, so the user’s privacy isn’t at stake. But, thanks to PSI and the hash preprocessing, the user doesn’t know what law enforcement is looking for.
But I’m not debating the merits of this engineering tradeoff - which seems fine, and pretty widely adopted - just its advertisement. The healthcare industry understands the importance of assessing clinical endpoints (like mortality) rather than surrogate measures (like lab results). Whenever we replace “legacy” with “cloud”, it’d be nice to estimate the change in TCO.