Mebibyte per second to Gibibit per second

dd uses binary units because Linux filesystems work in binary block sizes (4 KiB, etc.). Drive manufacturers use decimal MB/s because it makes speeds look about 5% higher and aligns with their decimal capacity marketing. A "550 MB/s" SSD shows roughly 524 MiB/s in dd.

Run "dd if=/dev/zero of=testfile bs=1M count=1024 oflag=direct" and it will report write speed in MiB/s. For read speed, use "dd if=testfile of=/dev/null bs=1M". The oflag=direct flag bypasses filesystem cache to measure actual disk performance.

No — 550 MiB/s is about 577 MB/s, and 550 MB/s is about 524 MiB/s. The ~5% difference means an SSD advertised at 550 MB/s will show around 524 MiB/s in Linux tools. It is not a defect or false advertising, just different unit systems measuring the same physical speed.

A RAID 0 stripe of two SATA SSDs gives roughly 1,000–1,100 MiB/s sequential reads. Four NVMe SSDs in RAID 0 can hit 12,000–14,000 MiB/s. RAID 5/6 arrays sacrifice some write speed for redundancy — expect 70–90% of raw stripe performance on writes.

Sequential reads let the drive stream data from contiguous locations, maximising throughput. Random I/O forces the controller to seek different addresses, adding latency per operation. An NVMe SSD might do 7,000 MiB/s sequential but only 50–80 MiB/s random (at 4 KiB block size), because the bottleneck shifts from bandwidth to IOPS.

At gibibit speeds, 7.4% represents a substantial amount of data. The difference between 10 Gibps and 10 Gbps is 737 Mbps — enough bandwidth for several 4K video streams. When designing storage fabrics or HPC interconnects, misinterpreting the unit can lead to underprovisioned systems.

PCIe specifications are actually defined in GT/s (gigatransfers per second) with specific encoding overhead. PCIe 3.0 uses 128b/130b encoding at 8 GT/s, giving about 985 MB/s per lane — which is closer to binary GiB/s than decimal GB/s. The industry uses both units somewhat loosely.

InfiniBand specifications use decimal rates (HDR = 200 Gbps, NDR = 400 Gbps per port). However, some HPC benchmarks and documentation convert to binary units for consistency with memory bandwidth figures. Always check the document's unit convention to avoid the 7% discrepancy.

Ordering a 100 Gibps fabric when you needed 100 Gbps means overpaying for 7.4% more bandwidth than necessary. Conversely, provisioning 100 Gbps when your workload needs 100 Gibps leaves you 7.4% short, potentially causing congestion during peak loads. At data center scale, these margins translate to real money.

Unlikely. Networking is firmly decimal (Ethernet, fiber optics), while memory and storage have binary roots. The two worlds overlap in storage networking, causing permanent confusion. The best practice is to always explicitly state "decimal" or "binary" in specifications rather than hoping everyone agrees.