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Everything I Know About SSDs

kcall.co.uk

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Re: Everything I Know About SSDs

#111

Post by toast0 »

ascar wrote: post #75
wtallis wrote: post #62

Earlier quoted context omitted.

> However, I'm not seeing conclusive proof that modern HDDs show performance variation with respect to radius. They definitely still do; it's fundamental to drives that run at fixed RPM but maintain high areal density across the entire platter. One of the 1TB drives I have lying around does about 183MB/s at the beginning of the disk, 148MB/s in the middle, and 97MB/s at the end.

I'm really interested in how you benchmarked that? Is there a "simple" way to specify the physical location on a HD data should be written to?

To build on the sibling comment, the simple way to benchmark this is with an empty hard drive, make a series of partitions in order:

1) start of drive partition

2) spacer

3) middle of drive partition

4) spacer

5) end of drive partition

Make 1,3, and 5 the same size, and then run raw disk benchmarks against them. The usual pattern is, like a record, the data begins at the edge of the platter and you'll get higher transfer speeds, and the end of the disk is in the middle, so slower there.

Re: Everything I Know About SSDs

#112

Post by guenthert »

notacoward wrote: post #2

The part about filesystems is slightly incorrect. > The way the file system handles this is incompatible with the workings of NAND flash. That's true of most conventional filesystems, but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them, and also why a typical flash translation layer bears a striking resemblance to a log-structured FS. There are also…

> but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them

I could swear I read such in 2010 -- did that actually happen in the last ten years?

Re: Everything I Know About SSDs

#113

Post by FpUser »

pkaye wrote: post #66
cattlemansgold wrote: post #8

There are a few technologies that I’ve tried very earnestly to understand, only to find out that it’s basically black magic and there’s no use in trying to understand it. Those things are modern car transmissions, nuclear reactors, and SSDs.

I used to work on SSD firmware for a long time. There is a lot of technology and individuals involved but to be honest I find learning on the present day web development stack more daunting at times!

That is because the firmware is all about efficiency and reliability is strictly business no f..ng around. This is at least from my experience.

Web is like: look ma, new shiny stack, gotta use it. The amount of tooling involved in creation of even simple things is often staggering without any real need for it. And often if you do not approach webdev in "politically correct" way you can be laughed out of the door.

Re: Everything I Know About SSDs

#114

Post by wtallis »

ls612 wrote: post #107
ololobus wrote: post #40

"As for writes, at 1 gb a day - far more than my current rate of data use - it would take the same 114 years to reach 40 tb." Maybe it works for author's very specific system or use-case, but on my personal MBP laptop with very occasional usage pattern--some days I do not use it at all during the week--I end up with 10 GB per day of writes on average. That way it will be 11.4 years already, not so many. And I do not…

I have an NVME SSD as a boot drive in my desktop and three years and change in (say 1200 days) it’s used 40tb of write (out of an advertised 400tb endurance so I’m not too worried). That works out to about 30gb of writes per day, which seems about right for medium to heavy use. I guess what I’m saying is that for modern SSDs I don’t think write endurance is a binding constraint in most cases.

For client/consumer SSDs, most vendors seem to view 50GB/day as plenty of write endurance for mainstream, non-enthusiast products. Virtually all retail consumer SSDs have a warranty that covers at least that much, and usually several times more for larger drive capacities (since write endurance is more often specified in drive writes per day).

Re: Everything I Know About SSDs

#115

Post by ryanmercer »

sn wrote: post #102

Things I've learned from using SSDs at prgmr: Since the firmware is more complicated than hard drives, they are way more likely to brick themselves completely instead of a graceful degradation. Manufacturers can also have nasty firmware bugs like https://www.techpowerup.com/261560/hp-enterprise-ssd-firmwar... . I'd recommend using a mix of SSDs at different lifetimes, and/or different manufacturers, in a RAID configu…

>I'd recommend using a mix of SSDs at different lifetimes, and/or different manufacturers, in a RAID configuration.

Oof, that's extremely obvious yet it never crossed my mind. Nice tip!

Re: Everything I Know About SSDs

#116

Post by ryanmercer »

computator wrote: post #44
cbdumas wrote: post #30

I love a minimal, text-only website as much as the next crotchety HN reader, but a little bit of CSS goes a very long way in terms of readability. Edit: Upon further inspection I see that this page was designed to be hard to read. Very curious.

If the author is reading this, I’d like to ask him to please run his article through a spell checker. All the effort to write a nice article is spoiled by having dozens of typos and spelling mistakes.

never realized how awful some of my own posts were with such errors until I ran my favorite ones through Grammarly after having paid for it last year to help me with writing a book draft (I abuse the hell out of commas apparently too, I blame Reddit).

Worse, some of them I'd sent to people dozens of times to read and there were these horrible typos cringe.

Re: Everything I Know About SSDs

#117

Post by osmarks »

guenthert wrote: post #112
notacoward wrote: post #2

The part about filesystems is slightly incorrect. > The way the file system handles this is incompatible with the workings of NAND flash. That's true of most conventional filesystems, but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them, and also why a typical flash translation layer bears a striking resemblance to a log-structured FS. There are also…

> but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them I could swear I read such in 2010 -- did that actually happen in the last ten years?

f2fs (https://en.wikipedia.org/wiki/F2FS) is now popular for Android-based mobile devices.

Re: Everything I Know About SSDs

#119

Post by rodgerd »

notacoward wrote: post #2

The part about filesystems is slightly incorrect. > The way the file system handles this is incompatible with the workings of NAND flash. That's true of most conventional filesystems, but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them, and also why a typical flash translation layer bears a striking resemblance to a log-structured FS. There are also…

He's also inaccurate in characterizing all cells as "1 or 0"; digital electronics have always been a cut-off of an underlying analogue value (such as voltage).

Re: Everything I Know About SSDs

#120

Post by labawi »

toast0 wrote: post #63
cattlemansgold wrote: post #43

Earlier quoted context omitted.

I guess what I meant is that the overall concepts are understandable. Nuclear fuel gets hot, boils water, drives a turbine. For transmissions, different sized gears allow things to turn at different rates. But as soon as I dive into the details, I get lost. How exactly can you control the nuclear decay? How exactly does do the gears in the transmission move around and combine with eachother to create a specific gear…

> How exactly can you control the nuclear decay? That's what the control rods are for. The uranium in one fuel rod in isolation decays at whatever natural rate, which would warm water but not boil it, and placing the rods near each other allows for the decay products (high energy particles) to interact with other fuel rods and induce more rapid decay. The control rods slot in between the fuel rods, and absorb the dec…

> The control rods slot in between the fuel rods, and absorb the decay products without inducing further nuclear decay. Usually these are graphite rods.

AFAIU graphite rods increase fission by slowing (not capturing) neutrons which in turn have a better chance of propagating further fission, because .. physics.

Quite nifty actually - without the moderator, the fuel wont burn.

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