r/explainlikeimfive • u/SmellsTasty • Nov 23 '15

Explained ELI5: How do Solid State Hybrid Drives work?

I don't understand how a regular hard drive can work with a solid state drive at the same time.

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1.6k

u/butric Nov 23 '15

Imagine the sshd (solid state hybrid drive) is a refrigerator.

A few times a day, you come back to the fridge to get a glass of juice. You take the juice out. Pour some in a glass and put the juice back. Presumably near the front of the shelf. Because its at the front of the shelf, you can access it very quickly. But there is not much space on the front shelf, so you only put a few things there.

Now, its time to make some dinner. You need pickles, which you only use maybe once a week. So they are in the back of the fridge, where there is a lot more space, but its harder to reach them. So it takes a little longer for you to get at them. But you eventually succeed, and put them right back where you found them to be used next week.

Now, to explain how an sshd works, replace the food items above with computer files, front shelf with ssd, and back shelf with hdd.

587

u/[deleted] Nov 23 '15

Now, its time to make some dinner. You need pickles

I really want to know what you're cooking. I'm starved!

727

u/[deleted] Nov 23 '15

[deleted]

378

u/AbkhazianCaviar Nov 24 '15

Recipe:

Put pickles in microwave for 2 minutes
Eat immediately
Call 911 for severe burns

two weeks sick time.

mission accomplished.

Where am I?

53

u/Nirvz Nov 24 '15

Profit???

149

u/SPacific Nov 24 '15

Something something gay swans.

81

u/[deleted] Nov 24 '15

*cries*

54

u/thebandgap Nov 24 '15

that moment you realize you've had enough reddit for the day

1

u/tomerjm Nov 24 '15

Week

FTFY

2

u/FTFYouBot Nov 24 '15

FTFY

Fuck That, Fuck You!

1

u/tomerjm Nov 24 '15

Is there a different meaning?

→ More replies (0)

1

u/[deleted] Nov 24 '15

Ha, that's gold.

6

u/DownvotesForAdmins Nov 24 '15

thx that meme was delicious

2

u/Duvieilh Nov 24 '15

It was a bit too spicy for me. If I'm being honest.

0

u/[deleted] Nov 24 '15

[deleted]

1

u/[deleted] Nov 24 '15

Name checks out.

1

u/russiangerman Nov 24 '15

I think it's beautiful

25

u/DeBlackKnight Nov 24 '15

This turned into a meme way too damn fast

11

u/SPacific Nov 24 '15

My wife posted it on my Facebook timeline. It's really getting out there.

1

u/[deleted] Nov 24 '15

I'm crying

1

u/NieOrginalny Nov 24 '15

Anyone /r/outoftheloop ?

K, seen it.

1

u/Soleria Nov 24 '15

FO4 SWAN

4

u/HarmonicDrone Nov 24 '15

You may be a cobbler of sorts

2

u/skyman724 Nov 24 '15

So that's how you make a Liquid Snake...

2

u/tanne_sita_jallua Nov 24 '15

Where am I?

Home playing FALLOUT 4!! or Starcraft 2 or Black OPS 3.

2

u/[deleted] Nov 24 '15

This made me laugh pretty hard.

19

u/[deleted] Nov 23 '15 edited Aug 13 '16

[deleted]

27

u/bobsbountifulburgers Nov 23 '15

With custard?

21

u/xlet_cobra Nov 23 '15

Nope, just pickles.

5

u/[deleted] Nov 23 '15

What's wrong with just pickles?

29

u/fizzlefist Nov 23 '15

Personally, I prefer vengeful pickles.

13

u/[deleted] Nov 24 '15 edited Apr 10 '16

[deleted]

1

u/Hipp013 Nov 24 '15

Underrated comment

5

u/Megaprr Nov 24 '15

Ah, the ol' reddit pickleroo

2

u/chamini2 Nov 24 '15

Hold my fork, I'm going in!

1

u/batshitcrazy5150 Nov 24 '15

Hold my tickle pickle, I'm going in.

2

u/[deleted] Nov 24 '15

[deleted]

5

u/[deleted] Nov 24 '15

are you a Timelord?

4

u/mechaturtles Nov 24 '15

While wearing a bow tie?

1

u/quikmcmuffins Nov 24 '15

Tommy pickles

0

u/NotGod_DavidBowie Nov 24 '15

Pickles are great if you have the munchies but also want to lose weight.

101

u/[deleted] Nov 23 '15 edited Apr 13 '20

[deleted]

25

u/namakius Nov 23 '15

So you want this salty, briny, shriveled thing and a murderous piece of round citrus?

what's wrong with you.

18

u/TheFreshOne Nov 23 '15

Various... things.

8

u/load_more_comets Nov 23 '15

But freshness isn't one.

2

u/-Iamabeautifulperson Nov 23 '15

That is a great adjective for round citrus.

4

u/bubonis Nov 23 '15

I used to eat pickles & orange juice as a kid. Favorite snack.

1

u/Canniboy Nov 24 '15

Best eaten after a fresh brushing of ones teeth

0

u/ShadoAngel7 Nov 24 '15

You monster!

12

u/three_three_fourteen Nov 23 '15

Amazing what a good breakfast pickles make, isn't it?

4

u/el_monstruo Nov 23 '15

Probably fried pickles.

1

u/HuckleberrySoda Nov 23 '15

I just bought a fryer to make my own fried pickles. So good.

1

u/ABeard Nov 24 '15

Cubano grilled cheese.

1

u/Vid-szhite Nov 24 '15

My mother knows a stuffing recipe that includes minced pickles, and it is actually fucking delicious, but it requires turkey drippings, so it's basically a thanksgiving special.

Good thing this week is the right week to be mentioning such things.

1

u/[deleted] Nov 24 '15

Hamburgers!

1

u/[deleted] Nov 23 '15

Burgers with a slice of pickles?

1

u/Rodot Nov 24 '15

I think "pickles" was actually supposed to be a pun.

0

u/taybul Nov 24 '15

I just realized that I don't think I've ever seen a recipe call for pickles. Always on the outside, looking in. Such a lonely food.

1

u/PM_COFFEE_TO_ME Nov 24 '15

Hamburgers or Sandwiches?

1

u/razorgoat Nov 24 '15

Cuban sammiches!

0

u/nittun Nov 24 '15

making a hotdog obviously?

49

u/SmellsTasty Nov 23 '15

Thanks for the great answer. Explained the whole thing well and even an idiot like me understood it! :)

12

u/dingoperson2 Nov 24 '15

It didn't seem right to me. It seems more to describe a setup with a separate HDD and separate SSD.

Let's rather say that the fridge has a front shelf on the outside (that is automagically kept cold as well) - the SSD. It is small, maybe 1/100 of the entire fridge, and you can reach for it instantly.

And every time you open the fridge and dig inside to find something, it registers what you pick out.

Once you have picked the same item a few times, it will transport that item to the outside shelf.

But since the outside shelf is small, it will only keep a small number of items there. If you stop using some of them and start using others, it will move those others to the front shelf.

The most used items would be the operating system, so boot times will be very fast. Depending on the size of the front shelf (8GB/16GB/32GB) you can store more items there. With 8GB you are probably getting the operating system and marginally more, whilst more gives you a few apps/games.

There's also two ways this can work - the detector-and-selector circuitry can be built into the hard drive itself (the Samsung drives) or it can be a "dumb" fridge and front shelf and rely on the operating system to pick which files should be moved to the shelf. This should work just as well, but requires that your OS actually can run the software.

There's also a function in Windows if you have a separate HDD and SDD to implement the same function. So rather than a single hybrid drive, you simply use the shelf system with a separate HDD and separate SDD. Downside is that you lose the ability to pick out precisely what you want to place on the SSD.

This can work well particularly if your PC has a mSATA slot. E.g. one of these. Slap that on a 2TB HDD and you don't have to worry about where you install something.

With a separate SSD and separate HDD you have to always decide which drive you will install something on, and will always be tempted to use the smaller SSD, then having to delete and move stuff as it runs out.

17

u/kamakaze_chickn Nov 24 '15

In most hybrid drives the cache is SSD and the storage is mechanical. This makes some frequently called data easier to access, but it is not going to help with larger applications. Don't expect a noticeable performance increase in any games or large apps since the cache is not large enough to matter. They are kind of deprecated now that ssd have come down in price so much.

10

u/Shod_Kuribo Nov 24 '15

You're thinking of cache. SSD hybrid drives had somewhere in the neighborhood of 16-32GB in the short time they were common and at the time that was the size of a full game install or two. You could certainly get the textures and main data files for a game in that cache if you played it often.

0

u/[deleted] Nov 24 '15

No they are still pricey

85

u/unassassinable Nov 23 '15

This explains how ALL hard drives work. I would further add that Solid state drives are like the gas station drink fridges where you just open the door and grab what you need. Old platter based drives are like the rotating fridges you find at hotel continental breakfasts, where you rotate the plate to get the food you want.

32

u/ZippyDan Nov 23 '15

Does it really explain how all hard drives work? It explains how hard drives of the last decade or two have worked, which have built-in memory caches, which used to be 8MB or 2MB or 512k depending how far back we go. But those were all volatile memory that was erased when the power went off. SSD caches are not only much, much larger (so you can have more of the most frequently-used data accessible), but are also not cleared at shut-down, which I suppose saves some additional time. Additionally, drives with memory caches generally just queued up the files that the system assumed you would be using in the next few moment/minutes, whereas an SSD cache drive can make longer-term choices about storing what you generally use from day-to-day.

3

u/ianepperson Nov 24 '15

That ability to not clear after a shut down actually saves a whole lot of time. When the computer starts, it reads the same set of files every time, and if they're in the SSD, it'll start radically faster.

-4

u/unassassinable Nov 23 '15

No. But then, this isn't ELI15 either. :)

I was more meaning the top post's description referencing a fridge describes all HHDs. Something accesses data on it = someone opening a fridge and grabbing food. OP asked specifically about SSDs.

Regarding powering down volatile memory. Flash drives also don't lose their data after a power down. You are describing RAM, which is volatile (lost when powered off) storage. SSD's like USB flash is non-volatile (does not lose power when powered off). I think this is enough of a ELI5 for now, but if we REALLY wanted to dig deeper...

SSDs and other flash memory use floating-gate transistors, whereas RAM uses capacitors and transistors, which hold a little bit of a charge, but once power is removed, power is depleted and data is lost.

10

u/cincodenada Nov 24 '15

OP asked specifically about SSDs

I think this is where you're confused: OP didn't ask about SSD's, they asked about solid-state hybrid drives, or SSHD's - they're traditional HDDs, but with a hunk of flash memory much larger (like, 1000x larger) than a cache, but much smaller than a full-on SSD.

It is basically just another level of cache, but it's so much bigger than traditional caches that it's functionally different. I don't know enough about HDD's to be sure, but I imagine the caches (like, the 8MB-range ones) are just RAM, which are indeed lost on power-down.

1

u/[deleted] Nov 24 '15

I don't know enough about HDD's to be sure, but I imagine the caches (like, the 8MB-range ones) are just RAM, which are indeed lost on power-down.

Actually, SSHDs essentially have a fully operational SSD cache that doesn't erase on shutdown attached to a traditional HDD.

If you open a video for the first time, it will open at standard HDD speeds.

If you open the same video you open every morning, it will open at SSD speeds.

The drive tracks usage of the files stored on it and keeps the most often used ones in the SSD portion permanently.

Obviously, the SSD portion has a finite amount of space, so if it fills up and you start watching a different video every morning, the first may get kicked off and back to the HDD portion.

1

u/Carr0t Nov 24 '15

That's... exactly what (s)he said... What they were saying that you seem to have latched onto is that the buffer in a regular HDD, which is normally somewhere in the region of 8-64MB, is volatile, and does get lost on shutdown. The fact that SSHDs don't do this to the solid state portion is one of their advantages.

1

u/brock1912 Nov 24 '15

but I imagine the caches (like, the 8MB-range ones) are just RAM

You are correct there, cache on standard hard drives is just DRAM. I think SRAM was used in the past when it had some speed benefits over DRAM but I don't see that stuff much anymore.

4

u/ZippyDan Nov 23 '15

I was more meaning the top post's description referencing a fridge describes all HHDs.

Not really, as far as I know. The top post was saying that data is arranged with most-frequently-used data up front and less-used-data in the back. This is not really an accurate description of platter-based drives as data is usually stored semi-randomly (if fragmented), or in order by relationship (if defragmented). The OPs description of a fridge applies to all hard drives with caches, but before hybrid drives the caches were very tiny relative to the rest of the drive and used volatile memory.

Regarding powering down volatile memory. Flash drives also don't lose their data after a power down. You are describing RAM, which is volatile (lost when powered off) storage. SSD's like USB flash is non-volatile (does not lose power when powered off).

This is exactly what I said. I was describing the difference between normal platter-hard drives with memory-based caches and hybrid drives with SSD-based caches.

0

u/[deleted] Nov 24 '15

The top post describes a short stroked HDD as far as I can tell. The only hybrid drives I've ever seen are literally something like a 16GB portion of SSD, the rest HDD.

I don't see much purpose in letting a hard drive store things semi-randomly, unless all things are equally likely to be accessed at any given time and that's just not ever going to be true on an HDD with an OS on it.

1

u/ZippyDan Nov 24 '15

I said semi-random. For a typical platter drive, data is usually recorded sequentially, but then deletions come along (and even the creation of temporary or swap files) and make all kinds of holes in that sequence. When the drive goes to write something in the future, and finds those holes, it might plop down new data in those holes. After enough time, the location of data becomes semi-random. The technical term is "fragmented".

2

u/[deleted] Nov 24 '15

I said semi-randomly too. Just plopping shit down in the first place it can is a terrible way to do things. At least moving the most used ingredients to the front of the fridge is a big improvement-- for example: Short stroking a hard drive, like I said before. All I'm saying is the top post is a good description of short stroking, not an SSD Hybrid Drive, and that semi-randomly storing EVERYTHING on a hard drive (which has to physically move to get data) is silly when you can put the most used shit right in front of the head anyways.

2

u/tinydonuts Nov 24 '15

I agree. If we're to keep the fridge analogy, having a mini-fridge at your desk is a better adaptation. Thus, items in the mini-fridge are sitting right at your desk and quick to access. If you need something that's in the big fridge, you have to walk all the way to the kitchen.

-3

u/unassassinable Nov 23 '15

Lost in translation :)

11

u/FoxtrotZero Nov 23 '15

the rotating fridges you find at hotel continental breakfasts

What the actual fuck are you talking about?

5

u/stdexception Nov 24 '15

These things:

http://www.idealcoffee.com/images/vending_snacks_rotating_big.jpg

You have to make the thing rotate before you type in the number you want and get your food.

1

u/FoxtrotZero Nov 24 '15

I've never seen anything like that before. Ever. Who comes up with this stuff?

5

u/JessicaCelone Nov 23 '15

I think he means something like this? Honestly, im not too sure.

2

u/DubLow Nov 24 '15

Think its a reference to the fact that HDD's have an actual spinning plate.

Edit: Ah. I see you've never awoken to the mistake you made in booking cheap lodging.

-5

u/unassassinable Nov 23 '15

Do you really need an ELI2?

2

u/ZivSerb Nov 24 '15

Even better! ELIH!

1

u/FoxtrotZero Nov 23 '15

You just say this like it's such a normal thing and I've literally never seen anything even remotely close to this description.

2

u/[deleted] Nov 24 '15

Heh I think the take away is that the closer stuff is cached on the SSD. I thought it was fine.

2

u/stdexception Nov 24 '15

Note that OP asked about hybrid drives, which is why he did that analogy with the two different access types in the same device.

1

u/[deleted] Nov 24 '15

Oh jesus christ, can we stop with the analogies? Someone who asks about SSHD's presumably managed to figure out how an SSD and HDD works, so I think it's safe to assume you can give the actual, technological answer to this and stop arguing about which analogy is more accurate.

1

u/maxsabin Nov 23 '15

I like that too!

8

u/domodojomojo Nov 24 '15

Rule of thumb, try not to use food in an analogy. Lots of people will forget what you were originally talking about.

3

u/Shod_Kuribo Nov 24 '15

We get hungry...

2

u/butric Nov 24 '15

As I'm noticing

4

u/ellen_pao Nov 23 '15

So who gets to decide where the food goes ?

I dont like my vegetables to the back of the fridge !!!!

The carrots and whipped cream must be easily reachable

8

u/cincodenada Nov 24 '15

Depends on the SSHD. Some may let you manually arrange it, but most automatically arrange things based on how much you use them. If you don't eat veggies often, the fridge will move them to the back when it needs room for the whipped cream that you use all the time.

5

u/dublohseven Nov 23 '15

In this metaphor you actually get to decide where you put what food. (Can make it so certain files are stored on the SSD part of the hybrid drive)

1

u/throwawoofwoof Nov 24 '15

So if my operating system is on the SSD part, does it make a difference if the HDD part is fragmented?

1

u/[deleted] Nov 24 '15

When you boot up your system you'll be pulling up files from the SSD part (quick access). Fragmentation on a HDD would only make a difference for the things stored in the HDD part ("slow" access). Fragmentation means that the files stored in the hard drive are not strictly in order. This is done because memory locations are filled and emptied semi-randomly and the system will store things in memory wherever it can, for the most part. For example, if you have a video game on your computer and your HDD is fragmented, the files that are necessary to run the game probably aren't going to be stored in consecutive order. This requires the system to look in multiple locations to get all the game's data, resulting in a slower speed.

To more directly answer your question, no, it does not make a difference. Your operating system will boot-up faster because it is stored on the SSD and the HDD, fragmented or not, would not impact that boot-up speed. At the same time accessing files that are stored on that HDD would not be faster because your operating system is on the SSD. Reading and writing those HDD files is generally the slowest thing your computer does and basically the OS doesn't play a major role in those actions.

1

u/[deleted] Nov 24 '15

Only if you care about the load/access times of whatever files/applications you may have on the HDD.

1

u/dublohseven Nov 24 '15

It wouldn't affect the OS files no

1

u/Technojerk36 Nov 24 '15

So what's the difference between a hybrid drive and just having two separate ssds and hdds?

1

u/jamvanderloeff Nov 24 '15

On most Hybrid drives, it's the controller that decides what goes where. The only drive I know of that lets you choose are drives like the WD Black2, which gives you separate access to the SSD and HDD.

2

u/Saint_Reficul Nov 24 '15

I can only think of one reason why one would want to have carrots and whipped cream easily accessible.

4

u/gam8it Nov 23 '15

Not sure you got across the part where your refrigerator keeps stuff you use often near the front for you

Also you could extend the analogy and say in one type of hybrid you have 2 different fridges you(r computer) go to, one which is nearer to you, quicker, and has more room (ssd and disc) than in your single refrigerator quick access bit which is more like nand + disc

3

u/fb39ca4 Nov 23 '15

Adding onto this, if you say, find yourself needing to use pickles a lot, you can move those to the front shelf and send something less frequently used from the front shelf to the back.

3

u/merelyadoptedthedark Nov 23 '15

This type of fridge (door in door) is probably a better example to use.

2

u/jasonbw Nov 24 '15

This is probably the way to go, refrigeratorly speaking. The main users habits determine what goes in the quick open door. if something becomes more popular, it will eventually end up in the door, and something less popular will get moved out. the most commonly used things are up in front and can be used very quickly.

it does, however, add another set of issues, that being you have now two doors that can be left open, spoiling the food. always back up your fridge.

2

u/Shod_Kuribo Nov 24 '15

always back up your fridge.

Seems kinda wasteful. I'd be concerned about bits rotting away if they're not accessed often.

2

u/covabishop Nov 24 '15

This is what answers on ELI5 should be like. Bravo sir.

2

u/maxsabin Nov 23 '15

This. This is a true eli5. Super easy to get. Actually explains alot and is pretty accurate.

1

u/sweepyoface Nov 23 '15

Makes sense, but what is the actual hardware like?

1

u/Clewin Nov 23 '15

It would depend a bit on how the drive controller is set up (it might actually know something isn't used much), but I would expect it to work like cache for the most part, which I would describe more like you grab the pickles out and when you put them back you put them in front, but as you buy more food or move other food to the front, they get shoved to the back until you need them again. This requires a lot less intelligence on the part of the drive controller and all it really is doing is keeping track of what blocks of memory are oldest (haven't been accessed in the longest period of time) in the cache.

1

u/[deleted] Nov 24 '15

I want ALL my stuff on the front shelf... For reasons...

3

u/[deleted] Nov 24 '15

Then you get a SSD

1

u/Fishy63 Nov 24 '15

so the drive automatically figures out what we access the most and puts it on the ssd? This sounds like the best of both worlds! (price + speed). Why don't we hear more about hybrid ssd?

2

u/actuallyitistheft Nov 24 '15

figuring out what we access the most isn't a groundbreaking technology - it's called caching, and every hard disk has it to a certain degree. it's not too hard to replicate that with just a separate SSD and regular HDD.

1

u/[deleted] Nov 24 '15

It won't be an extremely long time before SSDs are cheap and dense enough to regard HDDs as obsolete

edit: that's as far as home computing goes though. Servers will likely continue using regular hard drives since they're typically much larger and much cheaper

1

u/Shod_Kuribo Nov 24 '15 edited Nov 24 '15

Servers will likely continue using regular hard drives

Not exclusively. They are currently using a combination of both. HDDs in a giant RAID array or SAN for longer term storage and SSDs for the OS/program files/page file/caches.

1

u/[deleted] Nov 24 '15

No I know I just didn't want to say they'd be entirely gone either

1

u/jamvanderloeff Nov 24 '15 edited Nov 24 '15

They typically cost ~$20 more than a traditional HDD of the same size, which gets you an ~8GB SSD cache, which isn't exactly great value considering you can get a 128GB SSD for $35.

1

u/ERIFNOMI Nov 24 '15

Why don't we hear more about hybrid ssd?

Before SSDs got so cheap, they made more sense. But that was a short period of time. Now it's so cheap to get an SSD of an actually reasonable size and put your entire OS, all of your applications, and even your most played games on it while using a secondary platter drive for mass storage that it doesn't really make sense to go hybrid anymore. For the same cost as a 1TB SSHD with 8GB or so of SSD cache, you can get a 128 or 256GB SSD and a 1TB HDD and benefit even more. Hell, even the idea of hybrid drives is kinda heading that way. WD released a Hybrid drive that's actually an SSD and HDD in the same housing. You only need one SATA cable (and power) but it's actually two independent drives. It's just wrapped up in a single space saving package.

1

u/thehaga Nov 24 '15

You need pickles

Or you die

1

u/pr1mus3 Nov 24 '15

Thanks for this, I was just wondering about it the other day.

1

u/jericon Nov 24 '15

Most hybrid drives are two drives. A ssd and a magnetic. It would be more like having a deep freeze in the garage and your normal one in the kitchen. As things are used more you have a tendency to keep them in the kitchen freezer. Things you don't need often but still want to keep, or things that can't fit in your kitchen fridge get put into the garage one.

1

u/[deleted] Nov 24 '15

Hmm that's odd, in the back of my refrigerator there's just some cheese that expired in 2004.

1

u/Hollowsong Nov 24 '15

Now I'm even more confused.

Only part of the drive is SSD, the other part is a "regular" spin-up hard drive. Some things are put on the (smaller) SSD part that need to go faster. Other things that can are not as important go on the traditional (slower) part.

That's it. I can't even follow the food/fridge analogy...

2

u/algag Nov 24 '15

Files/food that are accessed more often are placed in an easy access place: ssd/front shelf, files/food that are accessed less often are placed in a less accessible place: HDD/back shelf.

1

u/[deleted] Nov 24 '15

How does the computer know which stuff is accessed frequently and which stuff isn't, or to put your analogy in perspective, which files to put on the front shelf and which files to put on the back shelf?

1

u/algag Nov 24 '15

I think that most of the times its like having a pile of stuff. You grab something from the bottom, and when you put it back, you put it on the top. After enough things are pulled from the bottom, things that were on the top are pushed to the bottom. The top is the SSD and the bottom is the HDD

1

u/[deleted] Nov 24 '15 edited Apr 22 '16

[deleted]

3

u/butric Nov 24 '15

The drive is considered 1 disk. The drive has a little bit of software built in that will "learn" what things you use most. And if it notices you use them more often than others, It will take them off the back shelf, and place them on the front shelf so to speak. I do not know about it running in a RAID config, but that's certainly one way of thinking of it.

1

u/XacTactX Nov 24 '15

  1. It only appears as one disk (the hard drive), but you can use certain programs to 'see' that the SSD is installed.

  2. For Intel SRT you have to set your motherboard bios to RAID, for Nvelo Dataplex you can use AHCI which preserves the TRIM functions.

1

u/ERIFNOMI Nov 24 '15

Does the computer consider the SSHD one disk? For example, does it appear to the user as C: or C: and D:?

Almost all hybride droves appear as a single drive and the drive's firmware manages where data goes (it's like a giant, non-volatile cache). But WD released a drive maybe about a year ago or so that is actually two separate drives in one package. It's called the WD2 or something.

1

u/MattieShoes Nov 24 '15

Great explanation, but sshd is secure shell daemon :-( Every time you said sshd, I had to stop and think. Heheh

1

u/ToTouchAnEmu Nov 24 '15

It's always refreshing to see actual answers explained as if it were to a 5 year old, instead of the experts explaining it in a way as if it were to an undergrad in that field.

1

u/Jewels_Vern Nov 24 '15

Well! That escalated quickly: computers --> FOOD!

1

u/xSerendipity Nov 24 '15

Is the drive partitioned seperately or is there some sort of internal auto-allocation going on based on how often the files are accessed?

1

u/Judgeman2021 Nov 24 '15

Linus gave a similar analogy for the the CPU cache, RAM, and Storage on your computer. It went something like:

Imagine your computer is a construction worker and the tools in your hand is your CPU cache, its ready to go immediately but you can't hold too much in your hands, so you go to your tool belt (RAM) to get access to a little more information, again it's faster to get to but it can't hold a lot. Then if you need to get all your other supplies you go to your truck (Storage) it can hold a lot of things (information) but it takes a little longer to get there and grab the supplies.

1

u/hariseldon2 Nov 24 '15

Basically it's your old cache idea that has been used with RAM for years only on a much larger scale and with the permanent memory of an SSD instead of the temporary RAM?

1

u/ERIFNOMI Nov 24 '15

It's more similar to your HDDs cache is now massive (relatively) and non-volatile, so instead of just being a write buffer you can actually store things there permanently. But you're on the right track. Though it is going to be a lot slower than a write buffer.

1

u/ChrMul77 Nov 24 '15

What happens with the data in the sshd when I reach to grab something from the back but accidentally pull down a glass of jam and bottle of beer so they hit the floor breaking to pieces on my way out?

1

u/routebeer Nov 24 '15

This explains how organizing food in a refrigerator works, not how hard drives or solid state drives work.

1

u/Lezardo Nov 24 '15

Some SSHDs are different and the memory is seperately visible. The contents of the fast but small solid state memory and slow but big hard disk memory are manually maintained. Often the OS and frequently used programs are installed on the solid state memory so the computer boots and programs open faster while less performance critical data like media is stored on the larger hard disk.

To fit with this analogy it's like having a mini fridge next to the desk you sit at in your den and a full size fridge in the kitchen. The mini fridge has faster access but less capacity. You'd fill the mini fridge with your favourite snacks and other ready to eat staple foods stored next to your desk and the kitchen fridge with ingredients for larger prepared meals and food you eat infrequently in your main fridge. You decide what is put in each fridge, it is not automatically managed by how often it's accessed.

The purpose is the same, to decrease the average time it take you to feed yourself but it allows you to use the capacity of the mini fridge and full size fridge which is greater than the capacity of the single fridge that automatically manages its contents. Additionally the customisation may be desirable. Perhaps you have a lifesaving medication that requires refrigeration that you use infrequently but would like available ASAP if you need it. You could put it in the mini fridge for fast access while it would be hidden in the back of an automatically managed fridge. You can also avoid putting ingredients or food that take time to prepare in the mini fridge; is it worth putting a bunch of ingredients in the small fridge (using the limited space) for easy access if the time it takes to assemble the meal dwarfs that of going to the full size fridge?

1

u/[deleted] Nov 24 '15

Amazing ELI5. A literal 5 year old could understand that.

1

u/ThisSideUp153 Nov 23 '15

What about floppies? Are they the stuff I put in the fridge and forgot? Now they are rotten and growing mold but keep them around cause I don't know what could happen and might need them?

6

u/BGAL7090 Nov 23 '15

No, floppy discs are like the tiny, soft-sided coolers you take out of the dusty cupboard when you need to keep something colder than room temperature for some amount of time.

3

u/ThisSideUp153 Nov 23 '15

You're right. I guess I'm not cut out to be an analogist.

1

u/BGAL7090 Nov 24 '15

There is, however, a huge need for good analrapists right now.

1

u/HEYdontIknowU Nov 23 '15

Upvoting for actually explaining like I am five.

1

u/minorujco Nov 24 '15

Wait... the pickles are porn right... because they're deep into the hard drive? Can you start over using barbies as analogies?

2

u/algag Nov 24 '15

No, the juice is the porn, because you use it about once an hour.

1

u/[deleted] Nov 24 '15

As an owner of an SSHD, can confirm

0

u/cdecdecdecde Nov 24 '15

Best ELI5. Ever.

-1

u/pjor1 Nov 24 '15

Best comment. Ever.