Sector interleaving - Revision history

Jnc: Clarify

2024-01-21T16:11:22Z

Clarify

Vaxorcist: Fixed typo

2023-07-31T20:07:43Z

Fixed typo

Vaxorcist: Usual Interleave Factors added

2023-07-31T09:37:49Z

Usual Interleave Factors added

Vaxorcist: New page "Sector interleaving"

2023-07-31T07:10:40Z

New page "Sector interleaving"

Vaxorcist: Created page with "'''Interleaving''' is a technique for speeding up access to sequential data on rotating magnetic media. Data is written and read sector by sector on tracks on Flop..."

2023-07-31T06:36:48Z

Created page with "'''Interleaving''' is a technique for speeding up access to sequential data on rotating magnetic media. Data is written and read sector by sector on tracks on Flop..."

New page

'''Interleaving''' is a technique for speeding up access to sequential data on rotating magnetic media.

Data is written and read sector by [[sector]] on [[track]]s on [[Floppy disks]] and [[Hard disks]].

In the past, read or write speeds were often faster than the speed at which the data could be processed (reading) or delivered (writing). If the sectors had been arranged one after the other on the data media, the following sector could only have been processed after a complete revolution. However, if space is left between two logically consecutive sectors for "later" sectors, multiple sectors can be read in one revolution. The process is called Sector interleaving, or simply Interleaving.

There are two ways to express the number of sectors skipped:

* The '''Skip Factor''' indicates how many sectors must be skipped in order to get to the next sector to be read.
* The '''Interleave Factor''' (or just '''Interleave''') indicates how many revolutions the disk stack has to perform in order to completely read a single data track.

While the Skip Factor is a positive pure number (0, 1, 2, ...), the Interleave Factor is usually given as a ratio, e.g. 2:1, or 3:1, meaning two respectively three revolutions are needed to read one data track.

The relationship between Skip Factor and Interleave Factor is simple:

Skip Factor = Interleave Factor - 1

Example: Interleave Factor = 3:1 => Skip Factor = 2

The disk controller, not the disk, sets the interleave factor. Some controllers can optionally implement different interleave factors at will. Choosing a wrong interleave factor degrades read/write performance significantly. Changing the interleave factor requires a low-level format.

@@ Line 1: / Line 1: @@
-'''Interleaving''' is a technique for speeding up access to sequential data on rotating magnetic media.
+'''Sector interleaving''' is a technique for speeding up access to sequential data on rotating magnetic media.
-Data is written and read [[sector]] by sector on [[track]]s on [[Floppy disk]]s and [[Hard disk]]s.
+It is useful because on [[floppy disk]]s and [[hard disk]]s, the time interval (for reading or writing), between the end of one [[sector]] on a [[track]], and the start of the next sector, was often less than the time needed for processing (reading) or delivering (writing) the data. If the sectors had been arranged with one immediately after the other on the data media, the following sector would already have started when the software went to deal with it, and so it could only have been processed after waiting a complete revolution of the  media, for the desired sector to come around to the [[head]] again. However, if space is left between two logically consecutive sectors for the 'next' sector, multiple sectors can be read in a single revolution of the media. The process is called 'sector interleaving', or simply 'interleaving'.
-In the past, read or write speeds were often faster than the speed at which the data could be processed (reading) or delivered (writing). If the sectors had been arranged one after the other on the data media, the following sector could only have been processed after a complete revolution. However, if space is left between two logically consecutive sectors for "later" sectors, multiple sectors can be read in one revolution. The process is called '''Sector interleaving''', or simply '''Interleaving'''.
+==Details==
 There are two ways to express the number of sectors skipped:
@@ Line 29: / Line 29: @@
 ==External links==
-* [https://en.wikipedia.org/wiki/Interleaving_(disk_storage) Wikipedia: Interleaving (disk_storage)]
+* [https://superuser.com/questions/1562649/whats-the-difference-between-sector-interleave-and-sector-skew-and-are-both-ev What's the difference between sector interleave and sector skew, and are both ever used on the same disk?]
-* [http://209.68.14.80/ref/hdd/geom/tracksInterleaving-c.html The PC Guide: Interleaving]
+<!-- * [http://209.68.14.80/ref/hdd/geom/tracksInterleaving-c.html The PC Guide: Interleaving] missing -->
 [[Category: Device Basics]]

@@ Line 21: / Line 21: @@
 * Interleave 3:1: <FONT COLOR="RED">1</FONT>, <FONT COLOR="BLUE">7</FONT>, 13, <FONT COLOR="RED">2</FONT>, <FONT COLOR="BLUE">8</FONT>, 14, <FONT COLOR="RED">3</FONT>, <FONT COLOR="BLUE">9</FONT>, 15, <FONT COLOR="RED">4</FONT>, <FONT COLOR="BLUE">10</FONT>, 16, <FONT COLOR="RED">5</FONT>, <FONT COLOR="BLUE">11</FONT>, 17, <FONT COLOR="RED">6</FONT>, <FONT COLOR="BLUE">12</FONT>
-Interleave Factor up to 4:1 were commonly used depending on controller capabilities.
+Interleave Factors up to 4:1 were commonly used depending on controller capabilities.
 The disk controller, not the disk, sets the interleave factor. Some controllers can optionally implement different interleave factors at will. Choosing a wrong interleave factor degrades read/write performance significantly. Changing the interleave factor requires a low-level format.

← Older revision		Revision as of 09:37, 31 July 2023
Line 21:		Line 21:
	* Interleave 3:1: <FONT COLOR="RED">1</FONT>, <FONT COLOR="BLUE">7</FONT>, 13, <FONT COLOR="RED">2</FONT>, <FONT COLOR="BLUE">8</FONT>, 14, <FONT COLOR="RED">3</FONT>, <FONT COLOR="BLUE">9</FONT>, 15, <FONT COLOR="RED">4</FONT>, <FONT COLOR="BLUE">10</FONT>, 16, <FONT COLOR="RED">5</FONT>, <FONT COLOR="BLUE">11</FONT>, 17, <FONT COLOR="RED">6</FONT>, <FONT COLOR="BLUE">12</FONT>		* Interleave 3:1: <FONT COLOR="RED">1</FONT>, <FONT COLOR="BLUE">7</FONT>, 13, <FONT COLOR="RED">2</FONT>, <FONT COLOR="BLUE">8</FONT>, 14, <FONT COLOR="RED">3</FONT>, <FONT COLOR="BLUE">9</FONT>, 15, <FONT COLOR="RED">4</FONT>, <FONT COLOR="BLUE">10</FONT>, 16, <FONT COLOR="RED">5</FONT>, <FONT COLOR="BLUE">11</FONT>, 17, <FONT COLOR="RED">6</FONT>, <FONT COLOR="BLUE">12</FONT>

		+	Interleave Factor up to 4:1 were commonly used depending on controller capabilities.

	The disk controller, not the disk, sets the interleave factor. Some controllers can optionally implement different interleave factors at will. Choosing a wrong interleave factor degrades read/write performance significantly. Changing the interleave factor requires a low-level format.		The disk controller, not the disk, sets the interleave factor. Some controllers can optionally implement different interleave factors at will. Choosing a wrong interleave factor degrades read/write performance significantly. Changing the interleave factor requires a low-level format.