Other secondary storage.
Sequential access.
Punch cards.
Punch tape - still used in some adverse environments.
Magnetic tape
Very slow but still economical for very large backups on large systems.
As drives get larger, advantages of tape vary.
DVD/CDROM
Cheaper
Small individual units 4.7GB/650MB.
Requires manual action or special software to track volumes.
Tape
Fairly high speed / high volume tapes available.
Although they cost.
200/400 GB $40 (2007) - Drive $1600
Much easier to automate.
Fewer separate volumes if correct size chosen.
Backing up to another drive may be cheaper.
May require opening system case. (techincal skill)
Or additional hardware (external USB2 case).
External may be fairly slow.
Floppy - Floppies are the most common portable secondary storage.
Cheap.
Portable - reasonably resilient.
Random access.
Moderate storage capacity.
Combined with compression software - up 2 megabytes.
Combined with spanning software - unlimited (20 meg practical)
Supported by all systems.
Uses MFM encoding.
Ferrite head - cheap.
Floppy technology
Floppies use a single magnetic film coated flexible (floppy) plastic disk.
Read/write head contacts media.
2 read/write heads
head 0 on bottom, head 1 on top and offset by 4 or 8 tracks.
Staggered write head sandwiched between two erase heads to keep
the data track small and well defined.
Media mounted in a plastic sleave or case.
Because of the head and encasing contact
Drive rotational speed slow to avoid friction effects.
But results in low data speeds.
Constant rpm drives.
300 RPM (most) or 360 RPM (5 1/4 HD)
Uses IRQ 6, DMA 2, I/O ports 3f0-3f5, 3f7 (reserved since orginal PC).
Unless system is "legacy free" and floppy has to be USB interfaced.
Uses track, sector, head addressing similar to hard drives.
Kb/s Kilobits per second
TPI tracks per inch
BPI bits per inch
8" Floppy specifics.
Obsolete, very low density storage.
Single sided, less than 160 K.
Mounted in a plastic sleave that touches media.
Drive mount clamps directly onto media.
Hole in media used to locate sector 1.
Read/write protection hole covered to write.
Read/write head access hole open (constantly exposed).
5 1/4" specifications.
Early versions - Single sided - 160-180K. Commodore, TRS80, etc.
Double sided (PC standard).
Double density (double sided) 360K
48 TPI - 40 tracks, 5876 bpi, 9 sectors, 300 RPM, 250Kb/s
Track width 0.0118" (TPI and tracks don't add up)
2 sectors/cluster.
High density 1.2 M
96 TPI, 9869 bpi, 15 sectors, 80 tracks, 360 RPM, 500Kb/s
Track width 00061", Higher Oersted magnetic media.
1 sector/cluster
Double density drives readable (and often writable) by High but
not usually the other way arround.
Mounted in a plastic sleave that touches media.
Drive mount clamps on a plastic reinforced hub.
Hole wears over time - requiring wider tracks to correct.
Hole in media used to locate sector 1.
Hole in edge of sleave covered to write protect.
Second hole in edge of sleave used to id high density media.
Read/write head access hole open.
3 1/2" specifications.
Currently in use. But being replaced by worm cds and zip drives.
Double density 720K
135 TPI, 80 tracks/side, 8717 BPI, 9 sectors, 250Kb/s, 300 RPM.
Track width 0.0045", 2 sectors/cluster.
Cobalt(ferrite ?), horiz. polarity.
OS manufacturers offered OS disks that violated the above standards.
These disks were readable but not copyable.
High density 1.4M
135 TPI, 80 tracks/side, 17434 BPI, 18 sectors, 500Kb/s, 300 RPM.
Track width 0.0045", 1 sector/cluster Higher oestrad magnetic media.
Cobalt, horiz. polarity.
Extra density 2.8M
135 TPI, 160 tracks/side, 34868 BPI, 36 sectors, 1Mb/s, 300 RPM.
Track width 0.0045", 2 sectors/cluster. Advanced magnetic media.
Cobalt, horiz. Barium.
Suspended in a hard plastic case.
Ideally, only read/write head touches media when in use.
Loose felt lining guided spinning disk.
Drive mount clamps on a metal reinforced hub.
Hub does not wear - closer tracks and more consistant locatiing.
Hole in metal hub used to locate sector 1.
Hole in edge of sleave covered to write allow.
Second hole in opposite edge of sleave ids high and extra density medias.
Read/write head access hole covered until inserted in drive.
Floppy problems.
Mounting / Unmounting.
OSes usually cache a drive's directory(s) to improve performance.
Because floppies are removable, possible to have the wrong info cached.
On systems like Linux,
Floppies need (past tense) to be mounted and unmounted between changes.
To automate this,
floppy drives use pin 34 (DC - disk change) to flag change.
Some manufacturers use pin 34 to flag a different condition.
On 16-bit systems (Win9x^), can cause a disk change to not be recognized.
Resulting in previously cached listing to be applied to the new floppy.
Most new floppy drives are hardwired to use the DC signal.
However, some use a jumper and you should be able to correctly set it.
Floppy problems.
Reserved FAT (file access table) sectors.
Early OS file tracking fairly simple and rigid in its structure.
2 fats included on each disk to offer some error protection.
The fat area on floppies was reserved upon formating storage.
Media Root Dir. Max. Root
Desc. Fat size Size. Entries
5 1/4 360KB FDh 2 sectors 7 sectors 112
5 1/4 1.2MB F9h 7 sectors 14 sectors 224
3 1/2 720KB F9h 3 sectors 7 sectors 112
3 1/2 1.4MB F9h 9 sectors 14 sectors 224
3 1/2 2.8MB F9h 9 sectors 15 sectors 240
Note
X-ray machines do not affect floppies.
Metal detectors do.
Zip drive
Successor to the Bernoulli drive.
100 Meg and 250 Meg (and 750 Meg).
Available with several interfaces. Parallel, IDE, SCSI, and USB.
All of which offer higher throughput than the floppy interface.
Hard case with wide chamber allows suspended media for minimal drag.
Written on one side.
Bernoulli effect cause flexible disk to draw up against read/write head.
Ideally with a small layer of trapped air acting to buffer head.
Because disk not pressed against read/write head,
faster rotation possible.
Although not clamped to head like floppy, contact still occurs and
wears media.
High speed rotation (2968 rpm), zoned tracks.
High quality head and magnetic media, so smaller domains (more).
Click of death - damaged media. Also damage disk was capable of damaging
other drives.
LS 120 (Floptical) Superdisk
A newer technology offers better data storage on a media similar
to the floppy.
Uses an optical track to more accurately position the read/write head.
Hard case with wide chamber allows suspended media for minimal drag.
Same size as 3 1/2" floppy. Drive was capable of reading both.
Metal in Gap head - more precise magnetic domains.
Magneto-Optical technology
Uses recording concepts similar to cd (reflected laser light).
Single sided media.
Magnetic field applied to area to be recorded.
Recording media powerful but resistant magnetic material - high
coercivity.
A very small laser spot applied to spot to be magnetized on opposite
side of magnetic head.
When heated material magnetizes and magnetic particles realign in a
specific direction.
A polarized laser is used to read dot. Depending on the alignment,
laser is either reflected or absorbed.
$10/GB (2007)
Magneto-optical properties.
1 - 9 GigaByte storage.
3 1/2 and 5 1/4 media.
Read technology similar to CD-ROMs
Much lower fatigue than CD-RW
Greater head distances than Hard drive.
More rugged.
Media portable
High coercivity makes media resistant to stray magnetic fields.
Longer life span of recorded data.
Less likely to damage when being transported.
Write operation slow because of response time of media.
Writes performed in two step.
1st pass -All bits written in one direction.
2nd pass - appropriate bits toggled.
Reads reasonably fast.
Newer models cabable of recording MPEG 2 streaming video.
Both passes now done in single operation.
Very expensive $300 - $2000 drive $100-$800 media. ($10/GB)
SCSI interface (high speed).
Others.
Iomega Jazz - 1 GB and 2 GB - discontinued.
Castlewood Orb - 2.2 GB and 5.7 GB.
Iomega Peerless - 10 GB and 20 GB - discontinued.
Iomega REV. - 35 GB(native) and 90GB(compressed)
- actually a hard-drive with sealed and removable platter.
($65/disk or $50/disk in quantity [2007])
Other secondary storage.
Several random access storage devices available.
Floppy drive.
Floppy Technology
8"
5 1/4"
3 1/2"
Zip drive (bernoulli)
LS 120 (floptical).
Magneto-Optical Technology.
Magneto-Optical Properties.
Sequential access.
Punch cards.
Punch tape - still used in some adverse environments.
Magnetic tape
Very slow but still economical for very large backups.
Floppy - Floppies are the most common portable secondary storage.
Cheap.
Portable - reasonably resilient.
Random access.
Moderate storage capacity.
Combined with compression software - up 2 megabytes.
Combined with spanning software - unlimited (20 meg practical)
Supported by all systems.
Uses MFM encoding.
Ferrite head - cheap.
Floppy technology
Floppies use a single magnetic film coated flexible (floppy) plastic disk.
Read/write head contacts media.
Media mounted in a plastic sleave or case.
Because of the head and encasing contact - (slow data access).
Constant rpm drives.
Uses track, sector, head addressing similar to hard drives.
Kb/s Kilobits per second
TPI tracks per inch
BPI bits per inch
8" Floppy specifics.
Obsolete, very low density storage.
Single sided, less than 160 K.
Mounted in a plastic sleave that touches media.
Drive mount clamps directly onto media.
Hole in media used to locate sector 1.
Read/write protection hole covered to write.
Read/write head access hole open (constantly exposed).
5 1/4" specifications.
Single sided - 160-180K or Double sided 360K
Double density (double sided) 360K
48 TPI, 5876 bpi, 9 sectors, 40 tracks, 300 RPM, 250Kb/s
High density 1.2 M
96 TPI, 9869 bpi 15 sectors, 80 tracks, 360 RPM, 500Kb/s
Higher Oersted magnetic media.
Mounted in a plastic sleave that touches media.
Drive mount clamps on a plastic reinforced hub.
Hole in media used to locate sector 1.
Hole in edge of sleave covered to write protect.
Second hole in edge of sleave used to id high density media.
Read/write head access hole open.
3 1/2" specifications.
Currently in use. But being replaced by worm cds and zip drives.
Double density 720K
135 TPI, 8717 BPI, 9 sectors, 80 tracks, 250Kb/s,, 300 RPM.
OS manufacturers offered OS disks that violated the above standards.
These disks were readable but not copyable.
High density 1.4M
135 TPI, 17434 BPI, 18 sectors, 80 tracks, 500Kb/s, 300 RPM.
Higher oestrad magnetic media.
Extra density 2.8M
135 TPI, 34868 BPI, 18 sectors, 160 tracks, 1Mb/s, 300 RPM.
Advanced magnetic media.
Suspended in a hard plastic case.
Ideally, only read/write head touches media when in use.
Loose felt lining guided spinning disk.
Drive mount clamps on a metal reinforced hub.
Hole in metal hub used to locate sector 1.
Hole in edge of sleave covered to write allow.
Second hole in opposite edge of sleave ids high and extra density medias.
Read/write head access hole covered until inserted in drive.
Zip drive
Successor to the Bernoulli drive.
100 Meg and 250 Meg (and 750 Meg).
Available with several interfaces. Parallel, IDE, SCSI, and USB.
All of which offer higher throughput than the floppy interface.
Hard case with wide chamber allows suspended media for minimal drag.
Written on one side.
Bernoulli effect cause flexible disk to draw up against read/write head.
Ideally with a small layer of trapped air acting to buffer head.
Because disk not pressed against read/write head not pressed, faster
rotation possible.
Although not clamped to head like floppy, contact still occurs and
wears media.
High speed rotation (2968 rpm), zoned tracks.
Click of death - damaged media. Also damage disk was capable of damaging
other drives.
LS 120 (Floptical) Superdisk
A newer technology offers better data storage on a media similar
to the floppy.
Uses an optical track to more accurately position the read/write head.
Hard case with wide chamber allows suspended media for minimal drag.
Same size as 3 1/2" floppy. Drive was capable of reading both.
Metal in Gap head - more precise magnetic domains.
Magneto-Optical technology
Uses recording concepts similar to cd (reflected laser light).
Single sided media.
Magnetic field applied to area to be recorded.
Recording media powerful but resistant magnetic material - high
coercivity.
A very small laser spot applied to spot to be magnetized on opposite
side of magnetic head.
When heated material magnetizes and magnetic particles realign in a
specific direction.
A polarized laser is used to read dot. Depending on the alignment,
laser is either reflected or absorbed.
Magneto-optical properties.
Oestrad
Curie point - temperature at which a material can be easily magnetized.
Kerr effect - magnetic field cause reflected light to polarize at certain
angle and also change brightness.
1 - 9 GigaByte storage.
3 1/2 and 5 1/4 media.
Read technology similar to CD-ROMs
Much lower fatigue than CD-RW
Greater head distances than Hard drive.
More rugged.
Media portable
High coercivity makes media resistant to stray magnetic fields.
Longer life span of recorded data.
Less likely to damage when being transported.
Write operation slow because of response time of media.
Writes performed in two step.
1st pass -All bits written in one direction.
2nd pass - appropriate bits toggled.
Reads reasonably fast.
Newer models cabable of recording MPEG 2 streaming video.
Both passes now done in single operation.
Very expensive $300 - $2000 drive $100-$800 media.
SCSI interface (high speed).