Riser cards carrying multiple M.2-2280 SSDs are nothing new, but Apex Storage went above and beyond with its new X21 board, which can carry up to 21 M.2 drives. The add-in-card is aimed at applications that take advantage of both high storage capacities and performance, including databases as well as machine learning applications. At maximum capacity and utilization, the X21 can hold 168 TB of M.2 storage, running at a peak sequential read/write speed of up to 31 GB/s.
The Apex Storage X21 is a dual-PCB add-in-card with a PCIe x16 interface that is based around an unspecified PCIe Gen4 switch system (ed: and what looks like 2 switches) covered with a large heatsink. The AIC has 21 M.2-2280 slots for SSDs, and using 8 TB M.2 drives it can offer up to 168 TB storage capacity when fully populated – and twice that once 16 TB M.2 SSDs become available.
Apex Storage says that when equipped with fast SSDs, an X21 will be able to offer sequential read speeds of up to 30.5 GB/s as well as sequential write speeds of up to 28.5 GB/s, fully saturating the PCIe 4.0 x16 interface and leaving behind all SSDs available today. The X21 riser card also promises over 10 million random read/write IOPS (7.5M read IOPS, 6.2M write IOPS) as well as an average latency of 79µs and 52µs for reads and writes, respectively.
In fact, given the total number of drives used, it is possible that even previous-generation SSDs with a PCIe 3.0 x4 interface will be able to guarantee extremely high performance in this setup. Still, to get the maximum performance and take advantage of the NVMe 2.0 protocol, Apex Storage recommends using drives with a PCIe 4.0 x4 interface and up-to-date feature set.
Of course, 21 M.2 SSDs consume a lot of power, so the card comes with two six-pin auxiliary PCIe power connectors that can deliver up to 150W to the card. It is unclear how much power the X21 AIC can suck from the PCIe slot as well, but in theory the combination of the two connectors and the slot can provide up to 225W to the drives, or a bit over 10 Watts per drive. The cramped card doesn't offer much in the way of cooling, however, so Apex Storage recommends using external fans that provide airflow of at least 400 LFM – essentially requiring a server-style blower configuration.
Apex Storage's X21 adapters can work in multi-card configurations provided that their host has enough PCIe Gen4 lanes. With a multi-card storage subsystem we are looking at up to 107 GB/s sequential read performance as well as 70 GB/s sequential write performance, which is comparable to throughput offered by all-flash-arrays that are typically considerably bigger.
Apex Storage did not touch upon availability timeframe as well as pricing of its X21 card.