without LRO (long range order) but with SRO (short range order).Slow cooling below Tmcrystalline→high reflectivity Ĭrystalline and amorphous recorded: amorphous Initial:crystalline R: high R: low Record Erase laser spot recorded mark.Rapid cooling:amorphous→low reflectivity.Temperature temperature Rapid cool Slow cool melting point melting point crystalli-zation point crystalli-zation point time time Energy amorphous activation energy low reflectivity crystalline high reflectivity Recording and erasing Low level:Heating above Tcr→slow cool→crystalline DVD-RAM: GeSbTe based alloy DVD±RW: Ag-InSbTe based alloy.High level :Heating above Tm→rapid cool→amorphous.Erasing is done by heating to Tcr(400 C) to crystallize. Recording is performed by heating above the melting point Tm (600C) followed by quenching to amorphous state. Rewritable:As grown amorphous state is initialized to crystalline state by annealing.UV coat Printed surface Protective layers Reflection layer Recording layer Substrate Land CD-RW Optical pickup Objective lens Tracking Servo Focusing Servo Quarter wave-plate Collimating lens Grating Polarization Beam Splitter Cylindrical lens Optical detector.Phase difference in reflectionπ:Destructive addition of reflected beams.λ=780nm →λ’=503nm (wavelength in the substrate).(2000.1) p.11 Increase of Areal Density in Optical Disks Aiming at 100 Gb/in2 using near-field technique.Hole-burning memory: Local structure change.Holographic memory: Photorefractive effect.Magnetic phase change between ferromagnetic and paramagnetic states.Phase change between ordered and disordered states.Physical phenomena used in optical disk technology Holographic memory, Hole-burning memory.Magneto-optical: MO, GIGAMO, MD, Hi-MD, AS-MO, iD-Photo.Phase change CD-RW, DVD-RAM, DVD-RW, DVD+RW, BD, HD-DVD.Direct read after write (Write once type).Α spot sized Spot size at the focal point Different physical phenomena are used for recording of the signal on optical disks.There are three categories of optical storage, i.e., read-only type, write-once type and rewritable type.Record density is determined by the spot size of the light beam, which is limited by the wavelength of the light and the NA (numerical aperture) of lens.Optical storage is a storage using light for read-out of recorded information.Let's retire BlackMagic's Disk Mark and embrance Amorphous Disk.Introduction to OptoelectronicsOptical storage (2) Prof. There's plenty of aspects that aren't covered, such as latency, burst performance, power consumed, and mixed random read/writes, but this is a massive step in the right direction for gauging SSD performance on macOS. Also, CrystalDiskMark measures IOPS (Input/Output Operations-per-second), which is similar but also a different measure of disk speed. Usually, an OS wouldn't have that deep of a queue, but the Q1T1 does mimic a singular request.
The default depth is pretty high for the test. CrystalDiskMark tests random reads and writes both as queued requests and single requests. Random Read and Write tests are as important, if not more so, as many SSDs can deliver fast maximum continuous read and writes but much less so for random small data blocks.
This is useful but only measures one aspect of an SSD, and doesn't necessarily mimic accurately how most disk interactions occur. So why am I always complaining about BlackMagic Disk Speed TestīlackMagic's Disk Speed Test only tests one thing, continuous throughput.
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While it isn't a direct port, it's heavily inspired by the famed and loved Windows utility, CrystalDiskMark. The first commenter on FaceBook pointed out that we finally have a good disk benchmark utility AmorphousDiskMark.
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Awhile back, I made a video about USBc and the classic Mac Pro but lamented yet ago the terrible benchmarking on macOS.