The DOS partition limitation is derived from the File Allocation Table (FAT). DOS uses the FAT to keep track of file addresses. The DOS FAT 16 is only capable of working with 32,768 bytes per cluster and no more than 65,536 clusters. If you multiply the two numbers together, you get the maximum partition size that DOS can use (2,147,483,648 bytes or 2048 MB {2,147,483,648 / 1024 2}).
A file system is a required part of the operating system that determines how files are named, stored, and organized on a volume. A file system manages files and folders, and the information needed to locate and access these items by local and remote users.
During the format of a volume you can choose the type of file system for the volume. When you choose the NTFS file system, the formatting process places the key NTFS file data structures on the volume, regardless of whether it is a basic volume or dynamic volume.
During format and setup of a volume file system on a hard disk, a master boot record (MBR) is created. The MBR contains a small amount of executable code called the master boot code as well as a partition table for the disk. When a volume is mounted, the MBR executes the master boot code and transfers control to the boot sector on the disk, allowing the server to boot the operating system on the file system of that specific volume.
Note: The partition table contains a number of fields used to describe the partition. One of these fields is the System ID field, which defines the file system, such as NTFS, on the partition. For NTFS volumes, the system ID is 0x07.
The figure NTFS Architecture shows the architecture of this process.
NTFS Architecture
The following table describes the components of an NTFS file system.
NTFS Architecture Components on an x86-based System
| Component | Component Description |
|---|---|
| Hard disk | Contains one or more partitions. |
| Boot sector | Bootable partition that stores information about the layout of the volume and the file system structures, as well as the boot code that loads Ntdlr. |
| Master Boot Record | Contains executable code that the system BIOS loads into memory. The code scans the MBR to find the partition table to determine which partition is the active, or bootable, partition. |
| Ntldlr.dll | Switches the CPU to protected mode, starts the file system, and then reads the contents of the Boot.ini file. This information determines the startup options and initial boot menu selections. |
| Ntfs.sys | System file driver for NTFS. |
| Ntoskrnl.exe | Extracts information about which system device drivers to load and the load order. |
| Kernel mode | The processing mode that allows code to have direct access to all hardware and memory in the system. |
| User mode | The processing mode in which applications run. |
Magic Boot Disk v2.0
Operating System: MS-DOS
Version: 2.0
This MS-DOS boot disk contains the following:
Download Magic Boot Disk v2.0:
Self-extracting boot floppy image: Magic Boot Disk — Floppy Creator v2.0
ISO image to burn a CD: Magic Boot Disk — ISO CD Image v2.0
HDDScan
License: Freeware
Author: Artyom Rubtsov
Operating System: MS Windows 2000/XP
HDDScan is a free low-level hard drive diagnostics tool.
HDDScan supports IDE/SATA/SCSI hard disk drives, RAID arrays, external USB/Firewire hard disks, flash cards.
The tool can scan the surface, view SMART attributes, adjust AAM, APM (Power Management), etc.
MHDD
License: Freeware
Author: Dmitry Postrigan
Operating System: pure MS-DOS (boot-floppy and boot-CD available)
MHDD is the most popular freeware program for low-level HDD diagnostics.
MHDD supports these interfaces: IDE, Serial ATA, SCSI. Also there is a possibility to access an USB storage, there are drivers for emulation (USB->SCSI).
This software can make precise diagnostic of the mechanical part of a drive, view SMART attributes, perform Low-level format, bad sector repair, different tests and tens of other functions.
Links:
MHDD FAQ
MHDD Documentation
Change log
Last version of MHDD, self-extracting floppy image
Last version of MHDD, CDROM iso-image
Last version of MHDD, just-an-archive (MS-DOS executables only, no SCSI support)
Magic Boot Disk with MHDD
MHDD 4.5 (older version, but includes ATA/SCSI Terminal):
MHDD 4.5, self-extracting floppy image
MHDD 4.5, CDROM iso-image
MHDD 4.5, just-an-archive (MS-DOS executables only, no SCSI support)
The goal of this post is to show you how a hard drive Printed Circuit Board(PCB) built. What are its main parts, how do they look and what are these parts names and abbreviations. As an example we are going to disassemble 3.5″ SATA drive.
To make it more fun we going to tear to pieces pretty new 1TB Seagate ST31000333AS hard drive. Let’s take a look on our “Guinea pig”.
Hard Drive PCB Main Parts:
The fancy piece of green woven glass and copper with SATA and power connectors called Printed Circuit Board(PCB). PCB holds on place and wires electronic components of HDD.
Now let’s remove PCB and see electronic components on the other side.
Hard Drive PCB Parts:
The heart of PCB is the biggest chip in the middle called Micro Controller Unit(MCU). On modern HDDs MCU usually consists of Central Processor Unit or CPU which makes all calculations and Read/Write channel – special unit which converts analog signals from heads into digital information during read process and encodes digital information into analog signals when drive needs to write. MCU also has IO ports to control everything on PCB and transmit data through SATA interface.
The Memory chip is DDR SDRAM memory type chip. Size of the memory defines size of the cache of HDD. This PCB has Samsung 32MB DDR memory chip which theoretically means HDD has 32MB cache (and you can find such information in data sheet on this HDD) but it’s not quite true. Because memory logically divided on buffer or cache memory and firmware memory. CPU eats some memory to store some firmware modules and as far as we know only Hitachi/IBM drives show real cache size in data sheets for the other drives you can just guess how big is the real cache size.
Next chip is Voice Coil Motor controller(VCM controller). This fellow is the most power consumption chip on PCB. It controls spindle motor rotation and heads movements. The core of VCM controller can stand working temperature of 100C/212F.
Flash chip stores part of the drive’s firmware. When you apply power on a drive, MCU chip reads content of the flash chip into the memory and starts the code. Without such code drive wouldn’t even spin up. Sometimes there is no flash chip on PCB that means content of the flash located inside MCU.
Shock sensor can detect excessive shock applied on a drive and send signal to VCM controller. VCM controller immediately parks heads and sometimes spins down the drive. It theoretically should protect the driver from further damage but practically it doesn’t, so don’t drop you drive – it wouldn’t survive. On some drives shock sensors used for detection even light vibrations and signals from such sensors help VCM controller tune up heads movements. Such drives should have at least two shock sensors.
Another protection device called Transient Voltage Suppression diode(TVS diode). It protects PCB from power surges from external power supply. When TVS diode detects power surge it fries itself and creates short circuit between power connector and ground. There are two TVS diodes on this PCB for 5V and 12V protection.
Tips: Hard Drive Failures cased by PCB can be solved by replacing a new one. How to find a matching pcb please refer to: How to find a Matching PCB
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