I think this is kind of a semantic bit. Higher capacity Macs have both slots filled, but the 512MB model just has 1. I don't think it is Raid 0 but more like JBOD. While read speeds go up the more space you have: 3400 at 512MB up to 8100 on 8TB, the write speeds seems to hover around 5500.
That is actually more evidence for the presence of a "RAID 0" like effect as opposed to the opposite (none and "just a bunch of independent disks).
Write lower than read is just a primary property of the low level NAND chip properties. Writes to NAND logic chips is dramatically slower than read. In some contexts whole blocks have to be rewritten even for a small , sub-block, change. Which means you have to read out the unchanged data to include with the block re-write along with the new changes. No way that is going to be as fast as read (which very hopefully) does not change the surrounding data at all.
Even more 'worse' when start storing 2,3, or 4 bits in each location.
As there are only two cards in there, it isn't like there is some way for there to be 5 different read speeds.
Of course there is.a way. The NAND packages for different capacities are not 100% uniform in construction. Some packages have more raw NAND dies in them than others. (so the number of dies 'talking' to is varying). Between differences in generation there is 'layers' in the NAND construction. (again number of channesl of flow changes).
The primary reason Apple is using two logical daughterboards to is to put more capacity by using the same level of density packages. Use more of the same NAND package as oppose to using a higher capacity density package. (typically a higher density package is more expensive as typically newer, bleeding edge tech). ( i.e, Apple can squeeze more economies of scale out of buy more of the same part in higher numbers. As opposed to more parts each in smaller numbers ).
The helpful side effect is that spreading out the capacity over more packages basically guarantees there are more memory channels that can be leverage in parallel ( e.g, a wider RAID-like stripe. The concurrent reads is faster than just two, or just one. )
They may not be normal SSD, but calling them SSDs is reasonable enough.
This is akin to calling a zebra a horse primarily because have seen more horses than zebras in your lifetime.
They are only close to being the same if don't pay attention to details.
Apple has decomposed a SSD into entirely dependent modules. The SSD controller is in the SoC. The NAND chips are either placed on the main logic board or on daughter cards. The daughter care a mainly just to efficiently add more NAND modules than would fit on a main logic board (some vertical stacking in systems that have more verticle clearance). And also cheaper for Apple. I suspect there are some customers for which the much easier to destroy daughter cards help decommission those Macs later with fewer problems ( where physical destruction of storage drive is the primary acceptable secure deposal of the data).
Putting the NAND chips on the main board or daughter board don't make them independently more useful . In both contexts they are basically useless as pragmatical 'storage drive' all by themselves. Like someone else pointed out it is like calling a platter from a hard drive a HDD. No read/write head , not controller, no metradata management.... it is not a 'drive'.
PCIE6 isn't on the market yet. Test cases don't count. Yes, they demoed it, but that doesn't mean it will be on the market soon. Maybe the next Mac Pro (which doesn't exist yet) will show up with TB6 (which also doesn't exist yet)
x4 PCI-e 6 bandwidth == x8 PCI-e v5 bandwidth == x16 PCI-e v4 bandwidth. A Mac Pro with a single x16 PCI-e v4 slot can handle a x4 PCI-e v6 drive with an appropriate card. All the card needs is a x16 PCI-e v4 to x4 PCI-e v6 switch and a slot to put the card into.
If spending > $10K on a workstation, it might be nice that can work with a single card in the next 2-3 years without having to replace the whole device. Also nice if can work with 2-3 PCI-e v5 devices which exist now. (don't have to wait... and carefully snipped from your quote. ). It isn't about the 'future' it is about now. The only thing the future brings is ability to do it with just one drive instead of 2-4 drives under some software/hardware RAID set up.
Pragmatically Thunderbolt is limited to x4 widths at any one generation. [ Primarily so that can fit onto a relatively affordable , copper wires in a classic USB style cable diameter] It is always going to be behind and one generation back.
And TBv6 likely his going to be hamstrung by USB committee foot dragging. TBV3 -> TBv4 wasn't bandwidth increases. It was far more making less USB optional loopholes smaller and the interface more consistent. Probably won't get to a Thunderbolt revision where there is a net bandwidth increase for more than two generations. And again it will fall behind. [ PCI-e v6 likely is also pragmatically shorter which is also in conflict with constraints that USB wants to deal with ]
This is the crux of it. Sure, if you happen to have $20 million to throw at the problem, you could buy that test drive from Micron. But, for those of us not playing golf with Musk and Bezos, TB5 is about as fast as anything we're likely to buy on the market, today.
Tomorrow? Well, that is another story.
It is today. ( x16 PCI-e v4 four M.2 PCI-e v4 cards exist today). PCI-e v5 drives are on market now. (now getting to 2nd , and soon 3rd , generation v5 drives on the market. )
Don' t have to stick to M.2 form factor either
The Kioxia LC9 offers 122.88TB of PCIe Gen5 NVMe storage in a 2.5" form factor for high-density and high-performance AI storage arrays
www.servethehome.com
2.5" enclosure has more space for more NAND packages so can 'fan out" and stripe more concurrent read/writes to fill the x4 PCI-e v5 connection.
And it isn't any more in terms of spend than a Mac Pro currently is; don't have to be anywhere near the $1M or even $100K range. ( go to general PC maket and spend money and not hard at all to get a M2. PCI-e
v5 right there on workstation motherboard. Not particularly new example:
" ... For connectivity, the TRX-50 SAGE WiFi comes with five PCIe x16 slots, three of which are Gen 5 enabled, as well as two PCIe Gen 5 capable M.2 slots, a single Gen 4 M.2 slot, and an additional Slim SAS connector for enterprise drives. ..."
Big chips require big power
www.tomshardware.com
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