SSHD vs. DRAM-less SSD?

[Newblesse Obblige]

They fill in between a HDD and a SSD with DRAM cache so which is better?

[.Apex.]

Just now, 5NibbaHertz said:

They fill in between a HDD and a SSD with DRAM cache so which is better?

How about neither, it isn't difficult to find a well priced SSD with DRAM

[jaslion]

The price difference between a dram less and a ssd with a cache is so minimal I see no point in ever going for a dram less ssd. That said the dramless will still be a bit better usually as tlc or qlc on it's own will give steady performance.

[WereCatf]

14 minutes ago, 5NibbaHertz said:

They fill in between a HDD and a SSD with DRAM cache so which is better?

Personally, I recommend against SSHDs. You basically have two drives in one, thereby double the chances of something breaking, and if either drive goes bad, they both become unusable.

[Jurrunio]

DRAMless SSD = the cache in an SSHD, why is this even a question?

[Newblesse Obblige]

On 3/16/2020 at 4:52 PM, Jurrunio said:

DRAMless SSD = the cache in an SSHD, why is this even a question?

On 3/16/2020 at 4:30 PM, 5NibbaHertz said:

They fill in between a HDD and a SSD with DRAM cache

:)))

[Newblesse Obblige]

On 3/16/2020 at 4:45 PM, WereCatf said:

Personally, I recommend against SSHDs. You basically have two drives in one, thereby double the chances of something breaking, and if either drive goes bad, they both become unusable.

its like a SSD used as cache(not as an normal drive) fused into a HDD?

so the separate solution(SSD cache + HDD) is more reliable than the fused version(SSHD)?

dont worry, i wont do this set up

[Jurrunio]

8 minutes ago, 5NibbaHertz said:

 

If you know that cache is faster, then of course a drive made entirely of cache (of an SSHD) is better, i.e. a DRAMless SSD. SSHDs are mostly (in Seagate's 3.5" implementation anyway) 8GB SSD + xTB HDD. Some better ones have 120GB SSD + 1/2TB HDD setup but that's as good as SSHDs have ever reached

[RejZoR]

No one buys useless SSHD's with pathetic 8GB caches. I frankly don't know why they even exist.

 

However, Hybrid HDD+SSD makes tons of sense. Just pair any HDD with any SSD using software like PrimoCache and you'll have massive and speedy storage where all data remains accessible even if SSD dies or if software stops working for whatever reason. You'll just end up having HDD only speeds then. Here, you can have like 6TB HDD paired to 256GB or 512GB SSD and it'll cache all of it on that.

[Newblesse Obblige]

41 minutes ago, RejZoR said:

No one buys useless SSHD's with pathetic 8GB caches. I frankly don't know why they even exist.

 

However, Hybrid HDD+SSD makes tons of sense. Just pair any HDD with any SSD using software like PrimoCache and you'll have massive and speedy storage where all data remains accessible even if SSD dies or if software stops working for whatever reason. You'll just end up having HDD only speeds then. Here, you can have like 6TB HDD paired to 256GB or 512GB SSD and it'll cache all of it on that.

would you still use a cheap SSD to be used a cache or not? 

[RejZoR]

Just now, 5NibbaHertz said:

would you still use a cheap SSD to be used a cache or not? 

Yes. Caching is a delayed process and 90% of the time it'll be doing reads from the SSD cache anyway. Even DRAM-less SSD should work fine imo as they are still excellent at reads.

[Newblesse Obblige]

2 hours ago, RejZoR said:

Yes. Caching is a delayed process and 90% of the time it'll be doing reads from the SSD cache anyway. Even DRAM-less SSD should work fine imo as they are still excellent at reads.

what size should i get? does size/capacity of the SSD matter?

[RejZoR]

10 minutes ago, 5NibbaHertz said:

what size should i get? does size/capacity of the SSD matter?

It should increase with size of the HDD. 2TB HDD with 256GB SSD worked great. I'd stretch that up to 6TB where I think going with 512GB SSD would be smart. With those big ass 10 or 12TB HDD's and more, 1TB SSD would be logical. They go cheap enough these days to accompany a super expensive massive traditional HDD.

 

More data you store, more you want to cache it, because if cache is not big enough, oldest cached data will be overwritten with newer one. And if that is happening too often, you're wearing SSD and negating the cache benefits. It's still possible to make 16TB HDD work well with 256GB SSD. You could still fit in there 2 massive modern games and caching never just copies whole data set into cache anyway so it wills till be able to cover many things. WAAAAAAY more than any SSHD with its pathetic 8GB SSD cache...

 

I just don't get it. If SSHD's got 256GB SSD caches, they'd actually be worthwhile components. With 8GB, they just make no sense even existing. What it would do is make system boot faster and that's about it.

[aisle9]

On 3/16/2020 at 4:30 AM, 5NibbaHertz said:

They fill in between a HDD and a SSD with DRAM cache so which is better?

My thoughts:

 

SSHDs were an almost adequate compromise option several years ago if you couldn't afford an SSD. I'm thinking back to 2015, when a 120GB SSD cost $80. Now? SSHDs have serious limitations:

• Price. Consider that if you want a brand new 500GB hybrid SSHD, you're looking at $50, and it's a crappy-ass 5400RPM drive. Yes, there are cheaper drives out there, including a 7200 RPM Seagate, but those are refurbs. For $10 more, you can get an SSD of the same capacity (more or less) and with DRAM onboard.
• Performance: Once you get past that tiny little bit of cache on the SSHD, you have a 5400 RPM mechanical hard drive. To repeat: you have just paid $50 for a 500GB mechanical hard drive. The $10 you save might seem like a good idea today, but when you're waiting 90 seconds for Windows to load, nope. But isn't that what the NAND cache is for? To house OS files for faster boot times? Well.....
• That f*cking algorithm: You don't control what resides on the NAND cache of the SSHD. In theory, Seagate uses an "algorithm" to determine which files are accessed most often and place them on that cache. The logic is that the files accessed most are probably going to be the OS, so they should go on the NAND cache, right? Right? Well, in theory, sure. In practice, God only knows what ends up on that cache, but comparing boot times for the ones I used to boot times for a regular old WD Blue or Seagate Barracuda, and compared to the boot times for actual SSDs, um, whatever's on that cache sure as hell ain't the OS.

I wouldn't even consider a hybrid drive in 2020. Laptop OEMs aren't touching them anymore. The price premium of an SSD combined with the performance of a 5400RPM mechanical drive doesn't make sense, and it never really did. SSHDs were something between a compromise and a cash grab by Seagate in particular to knife into a market that shouldn't have existed in the first place.

[NewMaxx]

14 hours ago, 5NibbaHertz said:

would you still use a cheap SSD to be used a cache or not? 

Caching and tiering are different, first of all. Caching is when you buffer incoming writes before committing them to the slower media while tiering splits files into multiple performance tiers with the most-accessed data being in the hotter/faster tier (SSD) for reads. SSHDs actually do both as they still have a small amount of DRAM for write caching, but the 8GB SSD portion acts like a tier for reads. Second, SSDs have SLC caching - which is again a write cache¹ - and optionally DRAM, however DRAM is used for metadata and not write caching on SSDs. There are some drives like the upcoming MiDrive that operate differently, though (which is tiered storage management). Tiering storage can have some caching (e.g. Storage Spaces defaults to 1GB) and caching can be used for reads (e.g. PrimoCache, or from RAM), but I'm simplifying for your specific question.

 

1. Future drives will have separate read and write SLC caches, here is Toshiba's patent for it from Oct 2018. You can read from SLC, the problem is that the controller wants to flush it ASAP and data that's in transition (folding) has a read latency penalty.