DRAM-less MLC vs. planar TLC with DRAM buffer? Which one do you think is better?

[cbn]

Based on the current crop of controllers and NAND which combination do you think is better?

If there is a caveat involved with your choice please post in this thread.

 

[hojnikb]

DRAM less with MLC any day of the week. Of course there are some caveats associated with having no DRAM (although some controllers got around that pretty well -- think sandforce).

Although i think its going to be TLC+ no dram going forward for budget solutions. Just look at sandisk, they are already doing it.

 

[BSim500]

Although i think its going to be TLC+ no dram going forward for budget solutions. Just look at sandisk, they are already doing it.

^ This. The obsession with "SSD's must match HDD's $ for $ at any cost" is driving everything down into mediocrity, so expect dram-less TLC anyway.

 

[hojnikb]

Hopefully decent controllers and 3D nand will make that combination bearable.

 

[greenhawk]

dram less units with some fancy caching will be it for the budget end going forward. No need to bet on that.


I just hope that there is enough demand for high end units still otherwise the whole market becomes about as exciting as the spinning metal collection. Lots of green/eco drives, crap all performance drives.

 

[cbn]

Although i think its going to be TLC+ no dram going forward for budget solutions. Just look at sandisk, they are already doing it.

You must mean the Sandisk SSD Plus and Z410:

http://www.tweaktown.com/reviews/7726/sandisk-ssd-plus-z410-sata-iii-review/index2.html

I had no idea these were DRAM-less SSDs (using Sandisk 15nm planar TLC and Silicon Motion SM2256S controller). In fact, at one time the SSD Plus was known to use MLC NAND and SM2246XT.

So with the ADATA Premier SP580 (Marvell 88NV1120 and Sandisk 15nm TLC) and Patriot Spark (Phison S11 and unknown TLC NAND) that brings the total number of DRAM-less planar TLC SSDs that I now know about up to four.

 

[cbn]

I just hope that there is enough demand for high end units still otherwise the whole market becomes about as exciting as the spinning metal collection. Lots of green/eco drives, crap all performance drives.

PCIe SSD controllers should help bring the bottom up.

One question I have though is how much NAND and DRAM (or DRAM-less) when compared to SATA 6 Gbps?

The PCIe controller will cost more (although there is a PCIe 3.0 x 2 planned from Jmicron (JMF815) and a PCIe 3.0 x 1 from Marvell (88NV1140) that should bridge the gap) but yet at the same time extract more performance from any given quantity of NAND (up to a point).

 

[bononos]

You must mean the Sandisk SSD Plus and Z410:
http://www.tweaktown.com/reviews/7726/sandisk-ssd-plus-z410-sata-iii-review/index2.html

I had no idea these were DRAM-less SSDs (using Sandisk 15nm planar TLC and Silicon Motion SM2256S controller). In fact, at one time the SSD Plus was known to use MLC NAND and SM2246XT.
.......

I thought you were mistaken until I checked and found a 2015 AT news article that it uses "SanDisk's second generation 19nm MLC NAND".

I think the Kingston UV400 TLC-Marvell 88SS1074 is a dramless design.

 

[hojnikb]

I think the Kingston UV400 TLC-Marvell 88SS1074 is a dramless design.

Any more info on that ?

 

[tweakboy]

TLC , the learning channel.

 

[VirtualLarry]

DRAM less with MLC any day of the week.

MLC, definitely. Although, I would go a step further, and suggest MLC with power-protection caps. (I'm running Crucial M500 and Intel 320 Series drives.)

Although i think its going to be TLC+ no dram going forward for budget solutions. Just look at sandisk, they are already doing it.

Wow, talk about adding mediocrity to mediocrity.

 

[VirtualLarry]

You must mean the Sandisk SSD Plus and Z410:

http://www.tweaktown.com/reviews/7726/sandisk-ssd-plus-z410-sata-iii-review/index2.html

I had no idea these were DRAM-less SSDs (using Sandisk 15nm planar TLC and Silicon Motion SM2256S controller). In fact, at one time the SSD Plus was known to use MLC NAND and SM2246XT.

Is the SanDisk SSD PLUS now a TLC drive? If so, is that the first time that a mfg has silently swapped an MLC drive configuration for a TLC drive configuration?

I never thought SanDisk would one-up Kingston in the "WTF were you thinking???" dept.

 

[hojnikb]

Others have done this as well. Intenso did this with their top drives (S8+MLC to S10+TLC)

 

[bononos]

Any more info on that ?

No, I was mistaken. Its not dramless.

 

[JimmiG]

I don't see why companies would be interested in releasing DRAM-less with MLC. You're cutting cost at the controller end, and then spending extra money for the NAND? Either it's a budget drive with every cost-cutting measure imaginable (TLC, no DRAM), or a mid-range/high-end drive for people who care about performance (MLC, DRAM).

Of course with 3D NAND we'll probably see both combinations, but TLC on 3D NAND isn't so bad (see the 850 Evo).

 

[hojnikb]

once you go below certain capacity points, it makes more sense to go with a cheaper controller without dram (like sm2246xt) coupled with MLC than TLC. With TLC you're bound to spend more on controller (requires better firmware and stronger ecc like ldpc).

On a >120GB capacity point you might save 1$ because on raw NAND but controller will cost you 1.5$ more because of TLC.

This is the reason why smaller chinese ssds still use mlc.

 

[redzo]

You are overthinking it!!!

1. DRAM-less MLC (sounds cheap)
2. planar TLC with DRAM buffer (sounds also cheap)

Because we are all cheap(at this specifications) the correct answer is:
which one is cheaper

 

[cbn]

You are overthinking it!!!

1. DRAM-less MLC (sounds cheap)
2. planar TLC with DRAM buffer (sounds also cheap)

Because we are all cheap(at this specifications) the correct answer is:
which one is cheaper

One thing that people have been concerned about with planar TLC NAND is data retention and read speed degradation:

http://forums.anandtech.com/showthread.php?t=2467748&highlight=

http://forums.anandtech.com/showthread.php?t=2473705 (So far the OCZ Trion 100 and 150 (which both use Toshiba planar TLC and Toshiba branded Phison S10 controllers) are doing well though, see post #10)

However, DRAM-less MLC also has a problem related to reads (but as I understand the situation this is not due to data retention issues with the NAND itself, but rather the lack of external memory):

1.)

According to the Tom's test of Sandisk Z400s (which uses SM2246XT), the lack of DRAM does a play a role at high queue depths for 4K read:

http://www.tomshardware.com/reviews...6-3.html?_ga=1.164490619.552404762.1465083782

Any operation involving random data is slow on the Z400s. SanDisk's 15nm MLC flash can't make up for the lack of high-speed DRAM, even compared to TLC-based SSDs. At low queue depths, where performance really matters, the Z400s isn't that much slower than the 120GB SP550, though.

2.)

http://www.tweaktown.com/reviews/6924/patriot-blaze-120gb-low-cost-ssd-review/index.html

Here were the results of the sequential read:

Notice only the Phison S9 drives (Patriot Blaze and Patriot Torch) are the ones with variation in min, average, and maximum read speeds. Here is what tweak town wrote about that:

The Blaze 120GB was unable to read sequential data at a consistent pace in our test. The Torch 120GB was the same way when we tested it. I think the lack of a DRAM buffer to cache the table data played a role in the wide separation between minimum and maximum performance.