[HN Gopher] Everything I know about SSDs (2019)
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Everything I know about SSDs (2019)
Author : fagnerbrack
Score : 93 points
Date : 2024-04-02 17:06 UTC (5 hours ago)
(HTM) web link (kcall.co.uk)
(TXT) w3m dump (kcall.co.uk)
| idle_cycles wrote:
| Two wonderful papers that are relevant: 1)
| https://pages.cs.wisc.edu/~jhe/eurosys17-he.pdf 2)
| https://www.usenix.org/system/files/hotstorage19-paper-wu-ka...
| dang wrote:
| Discussed at the time:
|
| _Everything I Know About SSDs_ -
| https://news.ycombinator.com/item?id=22054600 - Jan 2020 (185
| comments)
| eatonphil wrote:
| You might also be interested in this AMA we held on
| r/databasedevelopment with two NVMe developers from Samsung.
|
| https://www.reddit.com/r/databasedevelopment/comments/1afpez...
| thadt wrote:
| Thanks for hosting (and posting it here). I was reading the
| "What Modern NVMe Storage Can Do..." paper just yesterday, and
| this was a great followup.
| jmbwell wrote:
| I always thought 'flash' was a holdover from early reprogrammable
| ROM technology, non-volatile memory that you could erase by
| literally flashing a literal flashbulb over a little window on
| the chip. I would've sworn in a court of law that I recall this
| being called "flashable" memory, that erasing it was called
| "flashing" it, and reprogramming it in general was called
| "reflashing" in a sort of synecdoche. And I'd have assumed that
| this was the fundamental origin of what became _electronically_
| erasable ROM (EEPROM), which led to all the various NVRAM
| technologies we have now, with "flashing" sticking as the term
| for reprogramming it, even after you could do it electronically.
|
| It looks like the story these days is that someone at Toshiba
| thought up the name out of the blue. I'm skeptical!
| sgerenser wrote:
| I never heard of using a literal flash to reprogram EPROMs, but
| this wikipedia entry[1] makes your story for the origin of the
| term "Flashing" seem likely
|
| _EPROMs are easily recognizable by the transparent fused
| quartz (or on later models resin) window on the top of the
| package, through which the silicon chip is visible, and which
| permits exposure to ultraviolet light during erasing._
|
| [1] https://en.m.wikipedia.org/wiki/EPROM
| jmbwell wrote:
| It does look like all the references I can find point to
| engineers at Toshiba in 1980 coining the name, although
| Google ngrams shows some references to "flash EPROM" prior to
| 1980, so I can't help but wonder if the idea existed at least
| in some form prior to 1980
| monocasa wrote:
| Looking into it, those references look miscategorized. It's
| some Zambian national report that's talking about 0.18um
| processes (aka, 180nm) in the same paragraph, which
| wouldn't have come out until the very late 90s.
| radicalbyte wrote:
| These things were used in a number of computers from the
| early 90s, I have a few lying around for my Amiga.
| 0xcde4c3db wrote:
| Old-school windowed EPROMs need to be erased under a UV-C tube
| for something like 20 minutes. By comparison a flash memory
| block erase operation is practically instantaneous.
| ThrowawayR2 wrote:
| EPROMs were erased by many minutes of exposure to UV light, not
| a flashbulb, in a device called a UV eraser. I've never heard
| anyone refer to any operation on an EPROM as "flashing".
| jmbwell wrote:
| Yep, "UV eraser" confirmed by an elmer I know. A unit with a
| drawer and a timer knob, he says you'd typically set for 30
| minutes.
|
| He says he does recall people calling it "flashing," but not
| until much later, by which time it would have been actual
| "flash" memory.
|
| As for my own memory, I'm going to file this under Mandela
| Effect, cross-referenced under Things People Probably Told Me
| That I've Believed Since Before The Internet Was Available To
| Fact-Check!
| howard941 wrote:
| Programming the windowed EPROMS was called burning. Don't ever
| recall hearing anything about flashing them for programming or
| erasure.
| monocasa wrote:
| Yeah, exactly. 'Burning' itself being a holdover from PROMs,
| where you'd literally burn certain fuses in the array to
| select bits.
| d_sem wrote:
| Anecdotally this was also what was told to me by (now retired)
| electronic engineers who worked in automotive embedded systems
| in the 80's/90's. The term flash was related to the process of
| UV exposure to erase memory. This was also humorously explained
| to me as the beginning of the end for system performance. You
| didn't need to prove out your system when you could just update
| your hardware after the fact. In a world of over-the-air
| flashing we have come a long way from fixed design elements.
| canucker2016 wrote:
| I always thought that "flash" memory was named for EEPROM's
| erase speed compared to EPROM erase speed (less than a second
| versus 20+ minutes).
|
| EPROM has erase as the first word in the acronym, so everyone
| just said "erasing" the PROM when they put the chip in the UV
| eraser.
|
| Wikipedia lists finer differentiation between flash memory and
| EEPROMs.
|
| see https://en.wikipedia.org/wiki/EEPROM#Related_types
| password4321 wrote:
| I've heard SSDs are more likely to "fail fast".
|
| Can anyone recommended utilities that monitor and warn before SSD
| failures?
| caseyf wrote:
| For NVMe, if you get the SMART data with
| smartmontools/smartctl, you can inspect Percentage Used.
|
| "Percentage Used: Contains a vendor specific estimate of the
| percentage of life used for the Endurance Group based on the
| actual usage and the manufacturer's prediction of NVM life. A
| value of 100 indicates that the estimated endurance of the NVM
| in the Endurance Group has been consumed, but may not indicate
| an NVM failure. The value is allowed to exceed 100."
|
| for SATA/SAS SSDs, there is "Media_Wearout_Indicator" which
| hasn't been a particularly reliable indicator in my experience.
| magnetic wrote:
| My SSDs show SMART attributes, which can be used as a rough
| indicator of health, but really the only strategy I've found to
| work well for my peace of mind is to use redundancy.
|
| Concretely, I use ZFS with a zpool with 2 SSDs in a mirror
| configuration. When one dies, even if it's sudden, I can just
| swap it out for another one and that's it.
|
| My vulnerability window starts when the first SSD fails and
| closes when the mirror is rebuilt. If something bad happens to
| the other SSD during that time, I'm toast and I have to start
| restoring from backup.
| markhahn wrote:
| little hard to understand why it's worth explaining the details
| if you're going to gloss over the issue of endurance and erase
| cycle limits.
|
| if you do very little writing, you have nothing to worry about
| with SSD endurance. just read-disturb.
|
| do you do very little writing?
| Eisenstein wrote:
| Something useful to know that wasn't mentioned: SSDs will corrupt
| data if sitting for extended periods without being powered on and
| thus should never be used for cold storage.
|
| "There are considerations which should be made if you are
| planning on shutting down an SSD based system for an extended
| period. The JEDEC spec for Enterprise SSD drives requires that
| the drives retain data for a minimum of 3 months at 40C. This
| means that after 3 months of a system being powered off in an
| environment that is at 40C or less, there is a potential of data
| loss and/or drive failures. This power off time limitation is due
| to the physical characteristics of Flash SSD media's gradual loss
| of electrical charge over an extended power down period. There is
| a potential for data loss and/or flash cell characteristic shift,
| leading to drive failure."
|
| * https://www.ibm.com/support/pages/potential-ssd-data-loss-af...
| robotnikman wrote:
| Makes me wonder if those external SSD drives made by Samsung
| and WD/Sandisk take that into account and use different flash
| memory with better longevity without power.
| sgerenser wrote:
| Unlikely in the case of Sandisk, which is known for a recent
| bout of extremely unreliable external SSDs:
| https://arstechnica.com/gadgets/2023/08/sandisk-extreme-
| ssds...
| wmf wrote:
| If anything, I would expect consumer SSDs to use the
| cheapest/lowest grade of flash available.
| Lammy wrote:
| Relevant: Nintendo 3DS and Switch game carts go bad unless
| played https://news.ycombinator.com/item?id=39367506
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