Introduction to Service Area Emulation Technology

To start with, the concept of ‘Service Area (SA) Emulation Technology’ will be explained, which is also called

‘Hard Drive Firmware Service Area Emulation Technology’.

Emulation is used to describe a technology which duplicates (provide an emulation of) the functions of one system

using different system, so that the second system behaves like the first system. It also refers to the ability of a

computer program or electronic device to imitate another program or device. In reality, this technology has been

applied to virtual computer system networks, such as virtual partition, virtual workstation, and virtual storage system.

The virtual system is designed to accomplish a certain set of commands. The command set is used to reallocate the

calculative resources which also enable the isolation of software, hardware, data, network system and storage system.

Basically, the emulator is achieved by the emulation of the command set defined by desired system.

Emulator can be categorized into different types according to the objective simulated layers. Currently, there are 4

main types of emulations which are hardware emulation, logical emulation, software emulation and application

emulation. The Hard Drive Firmware Service Area Emulation Technology has been introduced here. This is a new

technology which is used to initialize the firmware information of a specific hard drive by loading predefined SA

resource file onto the memory of the external emulator. In another word, the hard drive will boot itself from the

information on the emulator rather than from the native firmware information. By using the SA emulator, user can

access the data area directly without repairing the corrupted firmware. This technology is quite similar to the Hot

Swap operation where the emulation of SA is achieved by a donor hard drive. Because of the nature of the adaptive

information, many modern hard drives are not facilitated themselves to achieve a successful Hot Swap operation.

But, by using an external SA emulator, this problem can be resolved.

A Hard Drive can be compared to a small computer. It employs microprocessors to control both the physical

behaviour of the various electro-mechanical components, and the logical operations that store and retrieve data as an

arrangement of the magnetic particles on the disk surface. This operation is completely independent of the operation

of the host PC. Like any computer, the hard drive needs its own software to control the operation of the

microprocessors, but unlike a PC this software is limited to the drive’s operational functionality, and is not (and

under normal circumstances cannot be) changed by the user. This hard drive ‘software’ is, as a result, more usually

referred to as ‘Firmware’. The firmware carries out a range of functions, from what might be termed ‘Analogue’

functions such as controlling the spinning of the disc and positioning of the read/write heads, as well as the ‘Digital’

functions used to pass data files to and from the PC, keeping track of the location and parameters of the data files

stored, and many, many more. Without firmware the drive is simply a collection of electronic components.

Just as the software on a PC can have problems, so the firmware can also cause a hard drive to fail if it becomes lost

or corrupted. Statistical analysis shows that up to 60% of hard drive problems are due to firmware failure. Firmware

problems can arise from a range of causes:

• Instability or failure of electronic components

• Accidental or inadvertent removal of power to the drive

• Deterioration of the magnetic response of the data recording surfaces

The latter cause is virtually inevitable over time, and the deterioration will accelerate the longer or more intensively

the drive is used. Additionally the disk manufacturing process is not 100% perfect and as a result disks will

commonly leave the factory already having problems with certain areas of the disk. These areas where the drive has

problems correctly reading data from the disk are known as ‘Bad Sectors’. Sectors that fail simply because the data

stored on them has become corrupted are known as ‘Logical’ bad sectors and these can be ‘repaired’ by re-recording

the data correctly or in the correct format, however areas with problems arising from the magnetic response of the

disk surface failing are known as ‘Physical’ bad sectors, and these cannot be repaired. Bad sectors of either kind can

occur both in the data storage area of drive, but also in a ‘reserved’ area dedicated to storage of part of the drive

firmware called the ‘Service Area’. User data area bad sectors can cause the loss or corruption of data files or

reduced performance of the drive, bad sectors in the firmware area can lead to the drive failing completely. As the

firmware area needs to be accessed every time the computer is switched on and every time drive is accessed, the

chance of bad sectors becoming a problem in this area is consequently higher.

Part of the data stored in the firmware Service Area is the so-called ‘P-List’. This is a list of known bad sectors

detected as part of the post-manufacture testing process. Any sectors recorded in the P or ‘Production’ List will not

be used for the storage of data, the firmware will automatically arrange the data around them. Additionally where

the drive firmware detects further bad sectors arising from the normal day-to-day use of the drive, these sectors will

be progressively added to a ‘G-List’ or ‘Grown’ list (again stored within the service area) and again these sectors

will be avoided, with the firmware arranging data around them. This process takes place automatically, with the user

largely if not completely unaware that it is being carried out.

Where firmware has suffered logical defects, the HD Doctor range of drive restoration tools can be used to diagnose

and repair such problems. However where problems arise that is mainly due to physical defects then recovery of

user data will be difficult if not impossible without the use of Data Compass.

As previously stated, bad sector problems only worsen every time the disk is accessed and the intensive read actions

required to attempt to recover usable files from a disk are likely to be particularly detrimental, with a vicious cycle

of ever increasing risk of data loss. On common approach used to overcome this problem is that of ‘cloning’. This

involves taking an exact image of the disk contents, and then recovering the data from this cloned image rather than

the original disk. Data Compass is particularly effective in producing such disk ‘images’ even from disks with

serious bad sector problems.

Where the firmware, or the individual portions of ‘microcode’ or ‘Modules’ that make up the firmware become

corrupted, this will often be indicated by either the drive not being detected correctly by the host PC (possibly

shown as incorrect drive model, or with incorrect capacity displayed), or by being not detected by the PC at all. The

HD Doctor tools can be used to correctly diagnose and repair such problems. The tool will allow the firmware

modules to be tested or their content examined visually for defects, and where they are found to have problems they

can be reloaded using ‘good’ modules obtained either from copies taken from matched ‘donor’ drives, or from

libraries of firmware available for registered customers to download. However the subject of firmware is a complex

one and firmware ‘architecture’ varies widely between different drive manufacturers and even between different

drive ranges from the same manufacturer. Thus it can be difficult for a technician to become proficient in firmware

repair without considerable experience or training.

Instances will also arise where firmware modules have been checked and found to be faulty and where, on uploading

known ‘good’ copies back to the drive and re-checking the modules, they are still shown to be faulty. After repeated

unsuccessful attempts to repair such modules, it may become rapidly evident that the faulty modules are arising due

to physical defects in the firmware Service Area. Such defects cannot be repaired, and would, until the arrival of

Data Compass have meant that drives suffering such problems would have been thought irrecoverable.

In Hitachi/IBM hard drives, once the corresponding resource files are loaded onto the RAM of the computer

manually, the emulator (Data Compass) will stimulate the crucial firmware modules (e.g. PSHT, RSVD, RESF,

RAMO, ZONE, SRVP) from the defective drive and try to create a link between the resource files and all the

working modules. Once the link is established successfully, the emulator will enable the access of the user data area,

in which case the drive will behave working properly.

You may see 2 different diagnostic results if you use the HD Doctor to diagnose the Hitachi drive with one of the

firmware failures mentioned above. The HD Doctor will check the integrity of the modules of Hitachi drives by

looking at the header and footer. The actual content of the modules will not be gone through due to there is no CRC

checksum algorithm exists on Hitachi drives. There is no way to tell if the actual content of modules is good or bad

unless checking manually. In another word, either logical defects or physical defects in service area will not be

detected by any diagnostic tools. Figure 1 shows the situation when the headers and/or footer of the modules are

corrupted where the HD Doctor is able to detect. Figure 2 shows the situation when there is nothing wrong with the

headers and footers. In figure 2, it doesn’t imply that the actual content of the modules are good if the drive is not

recognized.

Figure 1

Figure 2

The general diagnostic procedure for checking and restoring firmware modules of Hitachi drives is:

• Load the defective drive from external resource file (HD Doctor has integrated the resource files for

all the series of Hitachi/IBM laptop and desktop drives);

• Do a complete firmware scan;

• If the scan result shows the error modules, try to replace the corrupted modules from a donor drive;

• If the scan result shows no error modules but the drive is still not being recognized, it implies that

there are physical defects in one or more of the modules. Manually going through each module is

required to find out which one is damaged. When it is found, try to replace it from a donor drive;

• After the replacement, if the drive is still not being recognized, then do a firmware scan or manual

checking again. You may find the damaged module contains the ‘4040’ in a certain area, as shown in

figure 3. We classified this area as physical defect in service area.

Figure 3

• Load the drive from file again and try to view sector, as show in figure 4. You may find that the user

data area is accessible even without any replacement of damaged modules.

Figure 4

There is no way to restore the files from this kind of failure Hitachi drives until the SA Emulation Technology has

been introduced. As the arrival of Data Compass, it provides a complete solution for data recovery from Hitachi

drives. It also brings you into a new generation of recovering data without firmware repair.