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Comment by pmoriarty | Hacker News Reader

I wonder how their reliability is compared to a traditional spinning platter drive, for the typical workload of a desktop.

It would be nice if I could ditch the bulky spinning hard drive (or even SSD drive) and use a microSDXC card. I've tried that before, and while it did work, they quickly (within maybe a month or two) wore out and got errors on them. I can usually get at least 3 or 4 years out of a traditional spinning platter drive.

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The M.2 form factor gets you most of the way there. They're significantly smaller than normal HDD/SSD, and can cope with being used hard, unlike mickey mouse SD card stuff.

For anyone else wondering what the M.2 format actually is and what compatibility issues there are with it:

https://www.youtube.com/watch?v=opwON-7J_wI

I was going to say something about reliability.

As impressive as this feat is, and it really boggles the mind, I've had a large number of SanDisk MSDs fail on me before I switched to Samsung. I'm not very likely to switch back.

Conversely the only Samsung microSD card I ever had failed on me. I've also had some trouble with SanDisk cards from time to time. My general experience is that microSD cards are okay but I'm not at all happy about them.

I'm doing a project soon involving a Raspberry Pi. I've used rpi for various things before but the different thins time is that it's going to be installed at the location of a client. I am quite nervous that the microSD card will fail. For my own stuff I can easily write the image to a new card and it doesn't matter. But with a client where they expect the thing I'm making to work it would be painful to have it fail.

Is there some ready-made Linux distro for Raspberry Pi that is extremely small in size and which is made to load it whole self into memory and not write back to the SD card at all? It'd be extremely helpful to know about it if any such distro exists. Preferably it should be based on Rasbian just slimmed down and with logging etc removed. That way the kernel itself would be more reliable so that it won't crash randomly for reasons that have otherwise been fixed in Raspbian but which might not be in an independently maintained kernel.

I don't know what your requirements are, but look at making the rootfs read-only if possible. This is how a lot of consumer devices running Linux work.

https://hallard.me/raspberry-pi-read-only/

If you want reliability, don't get a Pi. Look at the selection of Odroids and use one of their emmc modules.

Not raspbian based, but tinycore[1] has a raspberry pi boot, the whole O's is loaded in to ram at boot

[1]http://distro.ibiblio.org/tinycorelinux/ports.html

First of all, it should be noted that it's now possible to boot from USB, bypassing the need for a microSD card, though the feature is classed as experimental:

https://www.raspberrypi.org/documentation/hardware/raspberry...

You could also use network boot:

https://www.raspberrypi.org/documentation/hardware/raspberry...

To answer your question directly, yes there are Linux distros that minimise/eliminate SD card usage. Aside from being able to mount the SD storage as a read-only device (like you can with live Linux CDs), there are some minimal distros that boot to RAM. One example is Tiny Core Linux:

http://tinycorelinux.net/welcome.html

Latest RPi build is was released only a few months ago:

For Pi Zero: http://tinycorelinux.net/9.x/armv6/releases/RPi/

For Pi 3: http://tinycorelinux.net/9.x/armv7/releases/RPi/

As a last bit of advice, there are quite a few different storage options available for the Raspberry Pi. Here's one that you may be interested in (you can buy the hard drive seperately if you didn't want to use the Raspberry Pi Zero):

http://wdlabs.wd.com/products/pidrive-node-zero/

With the higher density flash cells on the same surface area, one wonders about the heat dissipation (especially in mobile phones). This and the associated workload (read vs write) ultimately determine the lifespan of these cards.

Heat levels are indeed something these cards must ensure. I use the Samsung Evos in Blackvue dash cameras which will get up to 80-90c in the sun in the summer.

endure..

One of the issues is that the protocol used by an SD card isn't as efficient nor battle-tested as SATA. It might not be much of a problem with relatively low capacities in the handfuls of GBs but could cause problems as you go beyond that.

Flash memory is usually rated to what, order of 100,000 write cycles? But it has much better endurance on reads. If they aren't used as something like a pagefile, they can usually last awhile. But I guess it depends on the use case, and I'm assuming this will be similar to what exists now.

Maybe if you have an expensive high end enterprise SLC SSD. Consumers use the cheapest SSDs available and that's usually TLC with 5000 or less write cycles and soon we will be on QLC which will only have up to 1000 cycles. The more bits a cell stores and the smaller the manufacturing process the lower the amount of write cycles. 2D NAND hit a scaling brickwall and the only way to scale NAND is now to stack layers on top of each other.

Obviously SD cards are even worse than SSDs when it comes to reliability.

5K~10K was MLC 8 years ago[1], and there's evidence that some cheaper/smaller-geometry flash didn't even make it that far[2]

Now, it's more like ~1K for (good) TLC and closer to 100 for QLC. There are no official numbers I can find on TLC/QLC endurance or retention (besides a lot of handwavy and weasel-worded marketing saying it's "good enough"), but the degradation is exponential with the number of bits, not multiplicative, so one can make an educated guess.

[1] http://www.farnell.com/datasheets/1382714.pdf note date, and see page 3.

[2] http://pdf.dzsc.com/88888/2008422102742719.pdf also note date, and look at 3rd item in the revision history

Toshiba says their upcoming 3D QLC NAND will be good for about 1k P/E cycles. But like most recent P/E ratings, that's almost certainly given under the assumption that you're using LDPC error correction or something equally robust, so you can't compare directly to the ratings for older SLC NAND.

Huh, wow.

I was going off of the datasheets for flash chips I've been using, but I guess things are different for really high-density ones.

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