操作系統(tǒng)有責任高效地使用硬件對于磁盤設備(編輯修改稿)
2025-02-08 06:36 本頁面
【文章內(nèi)容簡介】 e of multiple disks working cooperatively. ? Disk striping uses a group of disks as one storage unit. ? RAID schemes improve performance and improve the reliability of the storage system by storing redundant data. ? Mirroring or shadowing keeps duplicate of each disk. ? Block interleaved parity uses much less redundancy. 22 2/9/2023 RAID Levels 23 2/9/2023 RAID (0 + 1) and (1 + 0) 24 2/9/2023 Disk Attachment ? Disks may be attached one of two ways: 1. Host attached via an I/O port 2. Network attached via a work connection 25 2/9/2023 NetworkAttached Storage 26 2/9/2023 StorageArea Network 27 2/9/2023 StableStorage Implementation ? Writeahead log scheme requires stable storage. ? To implement stable storage: ? Replicate information on more than one nonvolatile storage media with independent failure modes. ? Update information in a controlled manner to ensure that we can recover the stable data after any failure during data transfer or recovery. 28 2/9/2023 Tertiary Storage Devices ? Low cost is the defining characteristic of tertiary storage. ? Generally, tertiary storage is built using removable media ? Common examples of removable media are floppy disks and CDROMs。 other types are available. 29 2/9/2023 Removable Disks ? Floppy disk — thin flexible disk coated with magic material, enclosed in a protective plastic case. ? Most floppies hold about 1 MB。 similar technology is used for removable disks that hold more than 1 GB. ? Removable magic disks can be nearly as fast as hard disks, but they are at a greater risk of damage from exposure. 30 2/9/2023 Removable Disks (Cont.) ? A magooptic disk records data on a rigid platter coated with magic material. ? Laser heat is used to amplify a large, weak magic field to record a bit. ? Laser light is also used to read data (Kerr effect). ? The magooptic head flies much farther from the disk surface than a magic disk head, and the magic material is covered with a protective layer of plastic or glass。 resistant to head crashes. ? Optical disks do not use magism。 they employ special materials that are altered by laser light. 31 2/9/2023 WORM Disks ? The data on readwrite disks can be modified over and over. ? WORM (―Write Once, Read Many Times‖) disks can be written only once. ? Thin aluminum film sandwiched between two glass or plastic platters. ? To write a bit, the drive uses a laser light to burn a small hole through the aluminum。 information can be destroyed by not altered. ? Very durable and reliable. ? Read Only disks, such ad CDROM and DVD, from the factory
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