Solid State Drives (NAND flash) don't have platters or heads. They have pages and blocks. However, to keep your OS happy, they emulate the "Basic Disk" behavior of LBA sectors.
The disk has a small microcontroller that translates that LBA into a physical location (Cylinder-Head-Sector or CHS). This abstraction is brilliant because: basic disk
You cannot overwrite data on an SSD byte-by-byte. You have to erase an entire block (128+ pages) just to write a single page . This is why the TRIM command exists—to tell the SSD, "Hey, these LBAs are deleted, don't bother keeping them." Solid State Drives (NAND flash) don't have platters or heads
| You notice... | The likely basic disk reason... | | :--- | :--- | | | High queue depth of random I/O. The head is seeking non-stop. | | SSD is slow on writes | The drive is doing "garbage collection" because it ran out of clean blocks. | | Disk shows 0 bytes (RAW) | The partition table (MBR/GPT) is corrupted, or the boot sector is dead. | | File copies start fast, then stall | The disk's DRAM cache filled up. You hit the actual platter/flash speed. | The disk has a small microcontroller that translates
If your database is doing random reads across a spinning disk, you are waiting for that physical arm to dance back and forth. That is why fragmentation kills performance.