Data Recovery Blog

The most commonly asked questions about the system BIOS and its relationship to hard drives. The following will provide you with basic information beginning with the definition of a BIOS, to identifying key features found in various BIOS’s. The purpose of this document is to aid you in solving minor difficulties you may be currently experiencing.

1. What is Logical Block Addressing (LBA)?

LBA is a mathematical scheme for addressing sectors, beginning at cylinder 0, head 0 and sector 1, which is equal to LBA 1. This scheme linearly maps the drive until the final physical sector is reached. LBA is efficient because it reduces some system overhead by not having to convert the operating system’s LBA to the BIOS CHS and then back to drive LBA.

2. What is CHS?

CHS stands for Cylinders, Heads and Sectors, this is the conventional means for BIOS to communicate to the drive. CHS has a limitation of 1,024 cylinders, 16 heads and 63 sectors per track resulting in a maximum capacity of 504 MB.

3. What is the difference between Normal, LBA or Large mode?

Normal mode is the standard BIOS translation scheme. This mode does not support drives greater than 504 MB. Large mode is a generic translation scheme used by some BIOS’s to access drives up to 1 GB. Logical Block Addressing (LBA) mode is a more advanced method of translation than Large mode. LBA mode is a somewhat faster and can see drives up to 8 GB.

4. What if the BIOS does not support the full capacity of the drive?

There are three possible answers to this question:

Upgrade the BIOS for the computers motherboard or replace the motherboard.
Add an Enhanced IDE card that has its own BIOS that provides support for large hard drives.
Install a translation software product such as Maxtor’s MaxBlast software, they’re latest version is 9.06M.

Hard Disk Repair

System BIOS and Hard Drive Related FAQs (Part II)

DATARECOVERYUNION.COM16 years ago5 years ago02 mins

5. Why use software for translation?

Software translation is an effective, although non-conventional, means of translating large capacity hard drives so they can be utilized on older systems with older motherboards and BIOS’s. We use Maxtor hard drives almost exclusively, and they (Maxtor) furnish a driver made by StorageSoft, which is called MaxBlast. Instead of loading a driver in the start-up files, MaxBlast loads drivers before the operating system is loaded.

6. Can a hard drive be transferred to another computer without losing data?

Generally speaking no, but there are exceptions to everything. Usually there are no guarantees that a new motherboard’s BIOS will use the same translation scheme as its predecessor. We recommend that you back up your data prior to making any system changes. We also recommend that the hard drive be re-partitioned and reformatted once installed in the new system.

7. Can the translation mode or parameters in the BIOS be changed?

When a drive is partitioned, the operating system interprets the size of the drive via information provided by the BIOS. Changing the translation can cause permanent data corruption. If the original parameters are changed, they usually cannot be recovered without specialized drive manipulation software. If you do not have this software, we recommend that the hard drive be re-partitioned and reformatted.

Hard Disk Repair

Partition Record Technical Details

DATARECOVERYUNION.COM16 years ago5 years ago03 mins

Different operating systems have different Partition Type bytes. The most common DOS partition type is 6h, which is used for Primary DOS partitions greater than 32 Mbytes.

Here is a list of known (and suspected) partition type bytes:

00 Not Occupied
01 DOS, Primary Partition (12-bit FAT, <16MB)
02 XENIX root
03 XENIX usr
04 DOS, Primary Partition (16-bit FAT, >=16MB and <32MB)
05 DOS, Extended Partition
06 DOS, Primary Partition (16-bit FAT, >32MB)
07 OS/2 HPFS, Win NTFS, QNX ver 2, or Adv UNIX
08 AIX – boot
09 AIX – data, Coherent
0A OS/2 BtMgr
0B PRI DOS 512 Mbytes – 2 Tbytes FAT32 Win95, OSR2 & 98
0C EXT DOS 512 Mbytes – 2 Tbytes FAT32 Win95, OSR2 & 98
0E PRI DOS 32 Mbytes-2 Gbytes FAT16 Windows 95 & 98
0F EXT DOS 0-2 Gbytes Windows 95 & 98
10 OPUS
12 Compaq diagnostics partition
40 VENIX 80286
50 DiscWizard Starter Edition read only DOS partition
51 DiscWizard Starter Edition read/write DOS partition
52 CPM, Microport System V/386
54 DiscWizard Starter Edition non-DOS partition
55 Micro House EZ-Drive ® non-DOS partition
56 Golden Bow Vfeature partition
61 Storage Dimensions SpeedStor partition
63 UNIX – AT&T System V/386
64 Novell NetWare 286
65 Novell NetWare 386
75 PC/IX IBM
77 QNX POSIX partition
78 QNX POSIX partition (secondary)
79 QNX POSIX partition (secondary)
80 Minix (v1.4a and earlier)
81 Minix (v1.4b and later), Linux
82 Linux swap partition
83 Linux native file system
93 Amoeba file system
94 Amoeba bad block table?
DB Digital Research CPM-86, Concurrent DOS
E1 SpeedStor 12-bit FAT extended partition
E3 DOS read-only
E4 SpeedStor 16-bit FAT extended partition
F2 2nd DOS partition, some OEM customized DOS
F4 SpeedStor, large partitions
FE Lan Step, SpeedStor (partitions over 1024 cyl?)
FF UNIX bad block table partition

Related link: SCSI Sense Key Chart

Hard Disk Repair

What is the length of cable that I can use with a Serial ATA drive?

DATARECOVERYUNION.COM16 years ago5 years ago01 mins

Serial ATA cables are available in many lengths up to 1 meter. Minimum cable length is 12 inches, using shorter cables can cause timing, or noise interference on the cable. The same conditions apply to cables that are too long. Though the Serial ATA specification calls out supporting cable lengths up to 1 meter or 39.37 inches, PCB traces from the cable connection to the host and drive controllers ASIC, adds length to the bus.

Example: SATA drive installed with a 40 inch cable. PCB trace from Serial host connector to the serial hosts ASIC = 3 inches. The same 3 inch PCB trace applies to the hard disk. This configuration gives you a bus length of about 46 inches. If you are having performance or data corruption issues, try using a shorter cable or different manufacturer of cable. Cable quality can vary between vendors.

Hard Disk Repair

Tips for upgrading drive in Macintosh computer

DATARECOVERYUNION.COM16 years ago5 years ago06 mins

To upgrade the drive in your Macintosh computer, the first thing to consider is do you want to upgrade the internal drive or do you just want to add additional storage with an external drive?

Internal Drive vs. External Drive

An internal drive will generally provide much better performance on the computer and can be used to store programs and data. An external drive will be slower and suited for data only, however it provides portability and an easier installation.

Internal storage considerations

Internal drives come in several interfaces, Serial ATA (SATA), ATA/IDE (PATA), and SCSI.

Most newer Apple desktop computers use SATA interface. Below is a list of popular Apples and the interfaces used.

Desktops – Desktop systems use 3.5″ drives.
Mac Pro – SATA
G5 – SATA
G4 – ATA (most of these systems are limited to 128GB capacity, see Apple Care document #86178 for details)

Laptops – Laptops use 2.5″ drives. Due to the complexity of installations in laptops professional installation should be considered.

Mac mini – Not user serviceable, see external drives below for additional storage.

G5 and MacPro computers include the cable and rails needed to connect the drive, so no accessories should be needed, just a Phillips screw driver.

G4 computers may require an UltraATA cable with 3 connectors if you are adding a second drive to the computer. A Phillips screw driver would also be required for this installation.

External storage considerations.

External drives come in several interfaces, USB 2.0, IEEE 1394a, IEEE 1394b and eSATA.

Most Apple computers have a 1394 port which will provide enough performance for data backups, but many not provide enough speed for day to day use. For higher speed check if your computer has any IEEE 1394b ports. 1394b offers much higher transfer rates, this interface is offered on our Maxtor line of external drives.

Most older Apple computer G4 and prior used USB 1.1 which is very slow and would not be acceptable for backing up large amounts of data or for day to day use. USB is very popular for PC use, so these drives are the most common, but may not be a good match for an older Macintosh. Newer G5 and Mac Pro computers have USB 2.0 which would provide similar performance to 1394a and should be fine for backup usage. When looking at different external drives, check if the bundled software is compatible with MacOS. Some Seagate and Maxtor product lines are specialized for different markets, so not all drive features will work on a Macintosh if the drive was designed for a Windows PC market. Seagate and Maxtor drives that have a 1394b interface tend to be customized for the Macintosh users.

eSATA offers the best transfer rates for an external drive, however at this time eSATA is not a standard interface on Macintosh computers. So, eSATA would not be a good choice for use with your Apple.

External cables: USB drives include a USB cable so the box should have everything needed to connect the drive as long as the computer has an open USB port. Most 1394a kits include a 6 pin to 6 pin cable which works for desktop computers, but a 4 pin to 6 pin cable may be required for use with a laptop. Most 1394b drives include the 1394b cable, but be sure to check the listing of contents on the box to be sure.

Hard Disk Repair

Tips for Replacing a Drive from a Failed RAID

DATARECOVERYUNION.COM16 years ago5 years ago04 mins

There are several items to consider when replacing a drive from a failed RAID. If you are building a new RAID, then all drives in the array should be the identical model if at all possible.

However, if you must replace a failed drive, it can sometimes be difficult to find the same model if that model is out of production. Below are some tips to follow when selecting a replacement.

Note: Keep in mind that the controller may or may not allow different models in a RAID, so check the RAID controller documentation.

1. Product life: What is the expected life of the remaining drives? If the other drives are approaching the end of their useful life, then it may be time to replace the entire RAID.

2. Capacity: The replacement drive should be the same or higher capacity than the original drive. Do not just look at the capacity on the box, since a few megabytes could make the difference between whether the drive will work or not.

You should check the number of LBAs (or sectors) on the drive. Some RAID controllers will allow you to substitute larger drives if the exact capacity is not available, while other controllers require an exact match. Check with the controller manufacturer if the documentation doesn’t make it clear.

3. Performance: The replacement drive should match the performance of the remaining drives as closely as possible. If your failed drive was 15,000 RPM, avoid replacing it with a 10,000 RPM drive. RAID arrays depend on the timing between drives to write data. Thus, if one drive doesn’t keep up, it may cause the entire array to fail or at least experience irritating problems.

4. Interface: Make sure the replacement drive uses the same type of interface connection as the failed drive. If the failed drive used a SCSI SCA (80-Pin) interface then don’t try to replace it with a 68-pin SCSI interface. With Seagate products the last two digits of the model number indicate the interface.
For example:
LW = 68-Pin
LC = 80-Pin
The 80-pin LC drives are hot-swappable with backplane connections.

5. Cache Buffer: It is recommended that the cache buffer for each drive be the same value. Most RAID controllers will consider drives with mismatching cache buffers to be ineligible for addition to a striped or parity array.

Hard Disk Repair

Hard Drive Errors

DATARECOVERYUNION.COM16 years ago5 years ago03 mins

1. ‘No ROM Basic’ Error

When a partition is not set to the bootable partition. This usually occurs when the drive at one time was a slave and now has moved into the primary position. Verify that the hard drive has an “Active/Primary” DOS partition. This can be accomplished with the DOS FDISK utility. Boot your system with DOS system diskette, type “FDISK/MBR” and press [Enter].

Note: All data could be lost when performing this command.

2. ‘Not Enough Drive Letters’ Error

After adding a new device such as a hard drive or CD-ROM drive the system reports an error saying: “Not enough drive letters” or “Not enough drive letters available”

This issue is caused by the “LASTDRIVE” line not setup properly or defined in the config.sys file.

Solution:
You must edit your CONFIG.SYS file. This file is located in the root directory of your hard drive.

From a DOS prompt, C:\, type the command edit config.sys.
Once in the editor, either change the LASTDRIVE=line or add a LASTDRIVE statement greater than the amount of drive letters.
For example the line could be: LASTDRIVE=Z
Make sure to save and exit.
Reboot and the problem should be resolved.

3. ‘Bad or Missing Command Interpreter’ Error

DOS does not start because it cannot find the command interpreter (COMMAND.COM). If this message appears during start-up, either:

The COMMAND.COM is not on the hard drive.
A COMMAND.COM from a previous DOS version is resident on the disk.
A conflict exists between IO.SYS and MSDOS.SYS files.

To resolve this:

With DOS 6.0 a user can override the CONFIG.SYS by pressing either the F8 or F5 function keys during boot. This solution only works if the correct COMMAND.COM is in the root directory.
Reboot system with System Boot Diskette. After booting to the A: prompt, type “SYS C:” and press [Enter]. This will transfer the system files back to the hard drive.

Hard Disk Repair

Partition Offset Information

DATARECOVERYUNION.COM16 years ago13 years ago05 mins

Partition Offset Information is a simple, single file Windows utility you can run to read and display the starting LBA for every partition. This tool detects disk drives that report themselves as large sector drives, typically 4KiB sectors, and analyzes the starting sector of a partition to see if the logical file system clusters are aligned to the disk drive or not. The Partition Offset Information utility was written in 2005 when Seagate Technology developed disk drives with 1KiB sectors. These drives were never released to standard distribution.

What is 4K Sector?
Large‐sector describes using a sector‐size of 4096 bytes instead of 512 bytes per sector. To the host, the drive still has 512 byte sectors and no modifications to the BIOS/OS are needed at this time to address the data on the hard drive.

Why does the industry need to transition to 4K sectors?
Larger capacities per disk (areal density) have created a need for more format‐efficiency (the ratio of data to non‐data) on disks. Using 4096 bytes per sector allows for more data versus sector overhead (servo, address marks, ECC, etc) per byte, allowing the Hard Drive vendors to increase the capacity of a given disk by ~ 10%

Industry transition plans.
By Jan 2011, all hard disk drive (HDD) manufacturers will be supplying 4K drives. All software and industry manufacturing facilities must be capable of supporting 4K HDDs. Since the HDD looks like a 512byte drive to the host, the only real ramification is the performance impact of any misaligned writes on data partitions that are not 4K‐friendly.

Why the need to align partitions in a 4K‐sector drive?
The straight answer is to avoid performance penalty. As much as possible we want every partition to start with LBA offset that is aligned to drives physical 4k‐sector to reduce the performance impact. Writes to the disk that are not “aligned” (written on modulo‐8 sector counts) will require the HDD to first read up the original 4096 bytes, then merge the new write data with the existing 4096 bytes that are not changed, and then write that whole block of 4096 back to the disk. This causes an approximate 15‐20ms excess overhead per write command that is not aligned properly. The only impact seen is
during random write commands. There is no performance degradation when performing reads.

Which OS are affected by 4K sector?
Even though all operating systems will be seeing 512 byte sectors through the use of emulation technology on the drive controller only Windows Vista and Windows 7 are 4K sector‐aware, meaning they will automatically align the data partitions on 4K byte sectors boundaries, matching the hard drive’s physical sector layout. Linux and Mac OS are also 4ksector ‐aware.

Windows XP doesn’t have this 4K awareness, and since the OS creates the first partition at LBA sector number 63 (common case), all following data‐clusters will be misaligned, causing a noticeable performance impact. Each write process will now cause a Read‐Modify‐Write that introduces additional latency due to the required additional rotation of the hard drive. Drive imaging/cloning software will also be affected by partition misalignment in some cases if the software itself is not 4K‐aware.

Hard Disk Repair

Partition Offset Information (Part II)

DATARECOVERYUNION.COM16 years ago5 years ago02 mins

How to check if a partition is aligned?
Seagate has created a simple Windows utility, Partition Offset Information, to read and display the starting LBA for every partition. This tool can analyze the starting sector of a partition if it is misaligned or not.

In the example below, drive C: is a generic drive (ST9160823AS) with 512 bytes per sector. Drives F:, G: and H: are logical drives, all on the ST32000540AS which has a 4096 byte (4KiB) sector size and an Alignment of 0.

If the alignment on the ST32000540AS was 1, instead of 0, the display would look like this:

Notice: the the RED exclamation marks. These marks indicate that the Logical Volumes (drive letters) in this partitioning arrangement are not aligned with the physical sectors on the disk drive. Normal 4K disk drives will ship with Alignment 0. Drives with Alignment 1 and not typical and the example above is shown only for comparison purposes.

It is important to understand that the drive operates with the same reliability, but just a little bit slower when WRITING to the drive. It runs the same when READING which accounts for the majority of activity on a disk drive.

Useful link: Download Partition Offset Information

Hard Disk Repair

Will adding an ATA PCI Adapter card increase disk performance?

DATARECOVERYUNION.COM16 years ago5 years ago01 mins

It really depends if the motherboard on the system supports the transfer rate of the hard drive. For example, if the motherboard on the system only supports ATA 66 and the hard drive is ATA 133 the drive will downgrade the transfer rate limiting the transfer rate to ATA 66. Adding an Ultra ATA 133 PCI Adapter card will increase the performance of the drive because the drive in not limited to ATA 66 and can now operate at a ATA 133 rate. However, if you have a drive that is ATA 33 and put it on an ATA 133 PCI Adapter card, it will not increase disk performance because the drive is only capable of ATA 33.