A whole bunch of disparate remarks in response to various messages upstream.
I love SACD as an audio medium and wish it a long and prosperous life. The best part is versatility - MCH, Stereo, and Redbook CD in a single hybrid disk. The worst part, like all physical media, is the gradual but steady disappearance of support (availability of players, availability of both new and old pressings). On a different thread about Oppos, there was a depressing industry magazine link from 2017 that showed how much of a decline there had been in purchases of physical media. Together with the rapid rise in secure streaming of high quality audio and video formats, we will surely see an acceleration in the already currently declining physical media/player marketplace.
Which returns me to the need for archival backup of my physical media, the DMCA be damned. We should all keep in mind the tenuous thread of work and luck that led to our ability to backup SACDs (the person who reverse engineered it all on the PS3 thanks in huge part to the leak of master keys; the features in a certain Mediatek chipset and the open Linux environment running on them that allowed the exploit on a small subset of universal drives for extraction of DSD bitstreams). Similar stories exist for the other formats. I hope none of us pirate music or video, yet any of us who backup our own entertainment media are in violation of existing law (but unlikely to be held to account).
I worked professionally in physics with a lot of IT my entire career. Regarding backups, a backup is only a copy of unknown quality unless you periodically verify the contents. That can be casual (playback the audio or video and note problems) or rigorous (compare CRCs or md5sums, use an advanced filesystem like ZFS or btrfs and periodically perform scrubs, on hardware RAID schedule periodic scrubs).
SSD (flash memory) is not an archival medium! The charge in the individual cells of an SSD will leak out (quantum tunneling) over time. Your USB stick or fancy SSD drive is convenient, fast, and will fail to return your data if you wait a number of years. Magnetic disk is better for longevity, but I also have a number of older disks that have interfaces (SCSI, IDE, ATA) that are increasingly inconvenient to access on new computers due to lack of matching hardware. It’s unfortunately necessary to periodically migrate data from old to newer technology devices.
The various optical media (mini disc, magneto-optical, phase change, [CD,DVD,BD]-R/RW) all failed as viable storage for backup mostly because areal densities were limited by the wavelength of light used. Magnetic domains were (and are) steadily pushed to small fractions of those wavelengths. So you can cheaply buy a magnetic disk with 10^12 bits/in^2 storage density, but the best multilayer BD is stuck at 1/100th of that. Your hybrid SACD is roughly 1/1000th of that. Data rates (latency, bandwidth) are also tied to densities. That said, I do like and trust M-disc for long term archival storage of critical personal data (multiple copies).
I have a long, painful (as a programmer), and boring history with tape (7- and 9-track, QIC, 8mm, DLT, LTO, STK Redwood/Eagle/etc.). Tape is critical to large scale industrial computing (my last employer, Fermilab, had over 600 petabytes of online robotic storage by the time I retired). Other than the mini-QIC drive I used for a few years in the mid-90s, I’ve not since been tempted as a consumer to buy a drive and use tapes at home. I’m comfortable using the various data wrappers required for tape (tar, cpio, etc.), but I doubt that many here are.
For folks interested in DIY NAS, yes, RPI and similar SBCs work (after all, many Synology systems have been based on MIPS or ARM processors). I use SBC hardware from Radxa; they sell quad-SATA (raspberry pi) and penta-SATA (Rock PI) interfaces that can be used. I now have 4 DIY penta-SATA based ZFS systems that have been running for up to several years and have had no failures and no complaints. But this is not for the casual computer user.
In all seriousness, yes, my tape comment wasn't directed at most people. I PROBABLY should have made that clearer.
