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A detailed overview of hard disks and file systems, covering essential concepts such as hdd and ssd components, logical structures, data addressing, and boot processes. It explores key features like tracks, sectors, clusters, and slack space, offering insights into their functions and significance in data storage and retrieval. The document also delves into the intricacies of disk partitioning, boot types, and essential windows system files, providing a comprehensive understanding of the underlying mechanisms that govern computer operation.
Typology: Exams
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HDD ✔✔(Hard Drive Disk)
non-volatile,
records data magnetically
SSD ✔✔(Solid State Drive)
solid-state memory,
uses microchips,
expensive,
supports a restricted number of writes over the life of the device
Two memories:
(retains memory even w/o power)
(faster access)
Disk drive types ✔✔- Magnetic storage devices
(e.g., floppy disks, magnetic tapes)
(e.g., Blue-ray disks, CDs, DVDs)
electronically erasable programmable read only memory
(e.g., USBs, MP3 players, digital cameras, SSDs)
refers to the tracks (of all platters) of the same distance from the center
Platters:
Components ✔✔Platter --> Tracks --> Sectors
Track vs. Area vs. Bit (Density) ✔✔- Track density:
the number of tracks in a hard disk
the platters' storage capacity in bits per square inch
bits per unit length of track
Logical structure ✔✔The logical structure of a hard disk the file system and software used to
control access to the storage on the disk.
Influences performance, consistency, expandability, and compatibility.
Common file systems:
FAT, FAT32, NTFS, EXT, EXT2, EXT3, EFS
Hard disk interfaces ✔✔- ATA/PATA (IDE/EIDE)
Contents of a sector:
(sector number and location that identify sectors on the disk; status info of the sectors)
(the drive controller drives the read process using these fields)
(code that ensures integrity of the data)
(spaces used to provide time for the controller to continue the read process)
Bit vs. Nibble vs. Byte ✔✔- Bit:
binary digit
0 or 1
4 bits
8 bits
HDDs:
Sectors:
Advanced format ✔✔new hard drives are 4KB advanced format sectors
removes redundant header areas, lying between un-merged sectors
efficiently uses storage space by merging 512-byte sectors into one single 4KB sector
increases probability of unused space in a cluster,
reduces disk storage area,
reduces the unused area on the disk
HDDs:
Clusters:
Slack space ✔✔the area of a disk cluster b/n the end of the file and the end of the cluster
data storage space from end of a file to the end of the last sector of the file
data storage space from end of last sector of a file to the end of the last cluster of file
Lost clusters ✔✔when the OS marks clusters as used but does not allocate them to any file
a File Allocation Table (FAT) error
occurs when the user does not close file properly OR shuts down a computer without closing an application OR disk corruption
Bad sectors ✔✔a damaged portion of a disk
formed due to configuration problems or physical disturbances to the disk
when formatting a disk, the OS identifies unusable sectors and marks them as bad
if data is in a sector that becomes bad, then it might not be recoverable (recover with specialized tools)
HHDs:
Data addressing ✔✔TWO TYPES:
HDDs:
Disk partitions ✔✔Partitioning is the creation of logical divisions upon a hard disk that allows a
user to apply OS-specific logical formatting.
(OS, system area, other boot-required info)
(holds info regarding stored data and files)
BIOS parameter block (BPB) ✔✔a data structure in the partition boot sector
describes the physical layout of a data storage volume (e.g., number of heads, size of tracks, etc.)
BPB structure defines the file system structure
(different for each file system)
assists investigators to locate the file table on the hard drive
Master boot record (MRB) ✔✔the first sector ("sector zero") of a data storage device
stores info regarding the files on the disk, their location, size, etc.
almost always refers to the 512-byte sector or partition sector of a disk
consists of:
(describes up to 4 physical partitions)
(a small part of code; is loaded into the BIOS and executes to initiate the system's boot process)
used for:
only one partition of type 0xEE (EFI_GPT_DISK), which reserves the whole disk for the GPT structure
(provides compatibility with legacy tools that don't understand GPT format)
Boot & Boot types ✔✔booting:
starting a computer from a powered-down or off state
restarting a computer that is already turn on through the OS
Essential windows system files ✔✔- Ntoskrnl.exe
executive and kernel
executive and kernel with support for Physical Address Extension (PAE)
hardware abstraction layer
kernel-mode part of the Win32 susbsystem
Boot process:
Windows:
UEFI ✔✔1. CPU IN PROTECTED MODE:
a. SEC (Security) phase
initialize firmware
b. PEI (Pre-EFI Initialization) phase
initialize low-level hardware
c. DXE (driver Execution Environment) phase
