Mebibyte per second to Kibibit 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.

Because "kilo" was used to mean both 1,000 and 1,024 depending on context, causing real confusion. RAM manufacturers used 1,024 (binary) while network engineers used 1,000 (decimal). The IEC created kibi (Ki) in 1998 to unambiguously mean 1,024, leaving kilo for exactly 1,000.

Very few people outside of standards bodies and kernel developers. Linux kernel networking code sometimes uses binary units internally, and some IEC-compliant technical documents use Kibps. But consumer networking has fully standardized on decimal kilobits (kbps), making kibibits a niche pedantic distinction.

At the kibi/kilo level, only 2.4%. But the gap compounds — mebi vs mega is 4.86%, gibi vs giga is 7.37%, and tebi vs tera is 9.95%. A "1 TB" hard drive holds only 931 GiB in binary terms, which is why your new drive looks smaller than advertised in Windows.

Hard drives are built from sectors of arbitrary size, so decimal marketing (1 TB = 1,000 GB) is natural and makes drives look bigger. RAM is addressed in powers of 2 because of how binary memory chips work, so binary units (GiB) reflect actual hardware architecture. Neither side wants to change.

Almost certainly not. Networking adopted decimal (×1000) from the beginning because serial link speeds are clock-derived and have nothing to do with powers of 2. Ethernet has always been 10/100/1000 Mbps. Binary prefixes solve a storage problem that networking never had.