1. The Soul of your Computer
Hard Disk Drives
The Soul of your Computer

2. Mechanically Speaking
Individual Disks, or Platters
Read/Write heads for each platter on actuator arms controlled by servo motor

3. At arm’s length
Platters are made of aluminum (hence “hard”) with magnetic media on each face.
The read/write heads “float,” or fly, above the surface of disk
Read/Write head
Fingerprint
Media
Aluminum

4. Data Encoding We use “flux reversals” to signal a 1 or 0
This is serial (one bit at a time)

5. Encoding Methods Old methods: Current methods:
FM. Frequency Modulation. Bit/Timing/Bit
MFM. Modified FM. Timing after two 0’s
Current methods:
RLL. Run Length Limited. Use short patterns to represent longer ones. 1991
PRML. Partial Response Maximum Likelihood

6. Even more capacity Stand the magnets on their nose
Perpendicular recording:
Used in iPod, and starting to appear for us.

7. Moving the arms Stepper motors Moves arm in fixed amounts (angular)
Data transfer errors as motor wears
Thermal expansion errors
Needed to “Park” the heads over non-data area before moving drive
Floppy drives still use stepper motors

8. Moving the arms
Voice coil “motor”
Same idea as the cone of a speaker

9. Voice Coil
Don’t need to “Park” the heads – they move automatically when power removed.
No contact means no wear, no thermal issues, faster movement
Can use one disk surface for positioning

10. Data Storage Where will we put the data we want to store?
How will we know how to get back to that data the next time we want to use it?
It turns out that three values will get you positioned at a known spot. These three values are called…

11. Geometry
Every model of drive uses a different geometry – total frustration years ago
Three values used today: Heads, Cylinders and Sectors per track (CHS).
Two obsolete values: write precomp and landing zone

12. Heads
The number of heads (and thus the number of platters) the drive has installed
Two heads per platter – but a drive may use one head for its own use; thus we can have an even, or odd, number of heads for data use.

13. Cylinders Also called “Tracks”
If we hold the heads still for a moment and allow the platters to spin, the heads will describe a circle
Track
platter
Lots of tracks: use concentric circles (same center point, different diameter)
Platter !

14. Sectors per track
Slice each disk like a pie – each part of a track is called a sector
A sector holds 512 Bytes (or less) of data

15. The other two
Write Precompensation Cylinder. Where the data encoding distance changed
Landing Zone. Where the heads went when parked.

16. Talk to the drive
IDE. Integrated Device Electronics. Move the controller circuitry to the drive Replaced two separate pieces that were joined by two ribbon cables.

17. Talk to the drive, cont.
SCSI – Small Computer System Interface, that discussion is coming shortly…

18. IDE/ATA Started showing up around 1990
Originally just parallel interface, now called PATA – Parallel AT Attachment Interface
SATA – Serial AT Attachment Interface. Started showing up around 2003

19. Logical Block Diagram

20. PATA or IDE drives Western Digital and Compaq in 1989
Gave it to ANSI for formal specification
Used the AT BIOS routines and two drives up to 504MB (when a 10 MB was huge!)
Enhanced IDE (EIDE) in 1991
Ultra- DMA in about 1994

21. Physical Connection Here is the back of a disk drive: Jumper Block
40-pin connector
Pin 1
Power connection

22. The other end
“Controllers” (really just pin connectors)

23. Connecting Cable
40 pins and either 40 wires (Ultra ATA-33) or 80 wires (+40 grounds) for ATA-66,-100 and -133

24. Setting the Jumper
Because we can connect two drives, we need to distinguish between the two
“Master” and “Slave” – Typically we boot from Master drive, but could boot from Slave drive

25. Smaller than jumpers on motherboard
Jumper Location
Older drives had jumper location in different places on controller card:
Smaller than jumpers on motherboard

26. Another Drive
Jumper location on back of drive

27. If I don’t know… Look around on the drive for jumper block
Read the label
Go to drive manufacturer’s web site for information
Some drives have a “Single” setting that you have to use if only one drive installed

28. On a 40-wire cable ONLY
Drive to connector is optional:

29. ATAPI
Advanced Technology Attachment Packet Interface, part of ATA-2 per Michael
Allows CD, DVD and Zip drives to connect to IDE cable(s) and controller
Began at about 24x CD
Scott Mueller says it showed up in ATA-4
Higher capacities, support for two more devices (total of four)

30. Translation, ATA-2 Translates cylinder and head values
We know that 16*2 (32) is the same as 4*8 (32, again), so we fib to CMOS what the “Logical” CHS values are, not the “Physical” values
BIOS uses logical values, controller converts to physical values
Use “extra” bits to allow up to 256 heads

31. Sector Translation
Shift numbers by 16x

32. ATA-3
Added S.M.A.R.T. – Self-monitoring, Analysis, and Reporting Technology
In theory, it is to help predict when drive will fail, but it generally is not used

33. ATA-4 Introduced Ultra-DMA (does not use the old DMA controller)
Introduced the 80-wire cable (still 40 pins) – optional usage meant no usage
UDMA/33 – 33 MBps max transfer rate
1996 – 1998 timeframe

34. LBA Logical Block Addressing
Divide total number of sectors (C*H*S) to get “new” C, H values leaving S=63
(1024)(256)(63)(512)=8.4 GB
Both the BIOS and hard disk drive have to be capable of LBA

35. INT 13h Extensions to LBA Breaks the 8.4 GB limit
Collect a lot of the bits (plus some previously unused bits) to allow 2^28 address bits
Max drive size moves up to 137 GB
Around 2000

36. ATA-5
UDMA/66 – 66 MBps
80-conductor cable now mandatory else the drive slows down transfer rate; positions on cable are now standardized
1998 – 2000 timeframe

37. More on the cable ATA/66 requires an 80-wire cable.
Contrary to Michael, you CAN use ’66 drive and ’66 controller with 40-wire cable, it just runs slow but no data loss.
Actually, the BIOS will whimper at you at each startup about the cable.

38. ATA - 6
UDMA/100
LBA addressing from 2^24 to 2^48 sectors which breaks 137 GB limit
2000 – 2002
Mechanically, we are still at about 60 MBps from read/write head to controller card (on the drive). Add buffer on drive.

39. ATA - 7 Introduced SATA drives (-1 and -2; 150 and 300 MBps)
UDMA – 133; never made it to mass production

40. Drive Maximums Prior to 1995 – 528 MB Prior to Jan 1998 – 8.4 GB
BIOS CHS (1024,16, 63) limit
Prior to Jan 1998 – 8.4 GB
“Logical” heads to 256 (LBA)
Prior to Sept 2002 – 137 GB
Interrupt 13 (Int13) extensions; feed drive stream of addressable sectors
Now no limit with 2^48 bits (up from 2^24) but we stop at 2.2TB

41. SATA
Fewer wires (7) = thinner cable; Differential signals (+ and – voltage)
Up to one meter long cable (from 18”)
Point to point connection – one device per cable so no Master/Slave issue
Performance is issue: 150 MBps vs. IDE at 133; SATA-II at 300 MBps burst mode SATA III at 600MBps
Host Bus Adaptor – where SATA plugs in 20

42. Data
Power

43. ESATA connector

44. AHCI Advanced Host Controller Interface Windows Vista and later
Works with SATA HBA (host bus adapter)
Makes the drive show up in Computer
Enables native command queuing; disk optimization feature

45. SCSI Small Computer System Interface 1970’s by Shugart
Uses a “chain” approach – device to device to Host Adapter/Controller
Can be internal (68-pin) or external (50-pin); newest use 68-pin external
Apple (older) used 25-pin connector (SCSI-1)

46. Daisy Chain

47. SCSI ID Use a number to identify devices on a link
Can be any number (0-7 for SCSI-1); 0-15 for SCSI-2 or -3
Host adapter usually set to 7; boot device set to 0

48. Termination Easy – both ends of the SCSI chain
Most devices have termination built in; can cause fits getting termination correct
Do it wrong and device(s) won’t show up

49. Configuring CMOS
At first, we had to know, then type in, the CHS values for a drive – lots of hassle
Today, CMOS will get its information from the drive automatically – even SATA drives

50. Drive Types
Rather than Cylinders, Heads and Sectors numbers, use Types
We worked our way up to 46 different types, Type 47 was “User Defined” and we were back to CHS values

51. Type 47 (User) Screen

53. RAID 0 RAID 0 – Striping Two or more drives
Writes alternate between drives for speed
Both drives get same drive letter from system
Fast but not safe; one failure and all fails 10

54. RAID 1 RAID 1 (Mirror) RAID 1 (Duplexing) Two drives, one controller
same drive letter
writes are to both drives
Safe, one drive can fail, but slow
RAID 1 (Duplexing)
Two drives, two controllers
Writes are to both drives
Same drive letter
Faster and safer

55. RAID 5 RAID 5 – Striping with Parity Three or more drives
Writes alternate Data, Data, Parity; Data, Parity, Data; Parity, Data, Data
Any one drive can fail and system can “heal” itself 8

56. JBOD Just A Bunch Of Disks
Not RAID, but a way to use available drives to create a large “logical” drive ( = 90 GB to OS)
Another name for spanning
One failure = total failure

57. Hard or Soft RAID Use software RAID in XP for 0
Use hardware RAID for speed and 5
Gamers love RAID 0 (now) 6

58. Physical Installation
Power down the system
Determine the max size disk system will tolerate – may be in motherboard book
Look at existing drive(s) for capacity
Pick controller, make sure jumper is set, plug in cable, add power connector
Power on the system

59. Physical Connection Here is the back of a disk drive: Jumper Block
40-pin connector
Pin 1
Power connection 4

60. Does it show up in CMOS?

61. CMOS
Even a new disk drive will show in CMOS due to Autodetection. Thank you.
Automatically sets drive geometry and drive identification.
Make sure you got the ribbon cable correct, power correct and jumper correct for a PATA drive; cables correct for SATA

62. PATA and SATA

63. Boot Order Another CMOS setting, maybe its own page, or part of a page
This could look like:
IDE-0
IDE-1, etc. 4

64. Solid State Drives No moving parts ! No extra heat
No extra power drain – well not as much
Solid state can be used in both laptop and desktop systems
Form factors are typically 1.8-inch, 2.5-inch or 3.5-inch

65. Solid State Drives SSDs can be PATA, SATA, eSATA, etc.
SSDs that use SDRAM cache are volatile so need battery
SSDs can use multi-level cell (MLC) or single-level cell (SLC) technology
You don’t want to defrag a SSD.

66. Booting There is enough BIOS to boot from hard disk drives
There is enough BIOS to at least “see” CD/DVD drives; on older systems there might not be enough BIOS to boot from CD
New hard disk drives need to be partitioned and formatted before use.

67. Troubleshooting
It takes: jumpers, data cable, power and BIOS setup to work correctly
Reverse the data cable: Pin 1 to 40 and drive won’t show up in CMOS
Drive might show with reduced size due to CMOS limitations in older hardware