Words and their connotations can change their meanings over time...
I
first heard the term "WORM" (Write Once Read Many times) back in 1980
- used in the context of one time programmable non volatile memory. Back then
Intel was trying to convert manufacturers to use EPROMs (Erasable PROgrammable
Memories) in low cost OTP windowless plastic packages for production runs
instead of the more expensive ceramic packages used for development which had
windows enabling the devices to be erased in a UV light box and reused. The
plastic packages also had the advantage of being compatible with robotic
insertion - unlike the more brittle ceramic.
In 1986 I was hearing the
term "WORM" again, this time referring to the new generation of 5.25
inch optical disk drives which were hitting the market as long term archival
storage.
Then for over a decade the terms WORM and optical storage
were synonymous, although the fashionable technology of the time changed from
writable CD, then writable DVD, and now HVD (Holographic Versatile Disc).
Then
in 2003 - a new type of WORM wriggled into our consciousness - the idea of one
time writable tape backup. Introduced by Sony as a feature in its SAIT drives -
the concept seemed bizarre at first. But there were good commercial reasons
behind the idea. US laws governing the ways in which data had to be archived
created a guaranteed market for any data archiving technology which made
accidental erasure of data foolproof. Sony managed this with some flash memory
inside the tape cartridge which remembered that it had been configured as a WORM
device and prevented over-writes at the low level driver level.
I'm
going to introduce a new idea - and remember where you heard it first. Because
in a few years time this could be a multi billion dollar segment of the hard
disk drive market - which needs all the revenue it can get - as it's under
constant pressure from two main trends:-
- a capacity versus price technology curve which at
times has much in common with the type of cliff that lemmings (or venture
capitalists wedded to learning curve pricing) like to throw themselves off
- serious threat of obsolescence at the entry level
capacity end - by lower priced, lower power and more resilient flash disks.
My new WORM concept - which you may already have anticipated
by this point - is WORM HDDs.
There are many reasons why WORM HDDs will
come and are inevitable. The main one is that if hard disk drive technology is
to become the real replacement for tape storage - then cost per bit
competitiveness - which some vendors claim has already been established - is not
enough. HDDs will have to become available with true WORM capability - which
means they will have to include a mechanical switch which enables them to be
configured as WORM devices - and which over-rides driver level over-writes of
the files on the disk when the directory is full. This will require standards to
be set up so that drives from different manufacturers understand how they are
supposed to operate. That process could be managed by a current trade body like
IDEMA. Or it could be managed by a new
body set up for the purpose.
WORM HDDs will have to have some other
characteristics - such as the ability to power down - and power up by remote
control in a predictable way - otherwise the power consumption of Petabyte disk
archives will be horrendous. Some drives already do this. For WORM applications
- low cost, low power and high MTBF will be more important than high
performance. But we're already seeing many of these capabilities in newer
serially connected hard disk drives.
What about
reliability? How
will hard disk drives compare to optical media or tape - when you come to read
the data off them in 5 to 10 years?
Well - tape isn't exactly
maintenance free. If you don't rewind and rewrite the data from time to time
it's not guaranteed to stay there. And tape media can stick and jam. Similarly
optical media is subject to aging effects. If you take the unit of a hard disk
drive WORM repository as being a network connected RAID system rather than a
single disk drive - then the problem with long term data viability is easily
resolved. At some stage in the 5 to 20 year cycle - when it's no longer economic
to buy replacement drives - you just move the data onto another newer replicated
WORM HDD system.
WORM HHDs will have a number of advantages compared to
write many times disks. For example - the risk from viruses or administrator
error deleting large chunks of replicated data (which does already happen with
conventional RAID based disk to disk backup systems) will be eliminated. And
compared to WORM tape - the WORM HHDs will be faster to read and write.
They
will also have a FUD (Fear Uncertainty and Doubt) advantage compared to
newer optical storage technologies - in being proven. It sometimes takes several
years for the long term reliability of new storage media to be proven - and
often the extrapolated data permanence and error rates in past technologies
have been revised downwards following a few years of actual product experience.
And
finally, WORM HDDs have the same superficial advantage that almost guarantees
that the concept will be adopted. Like Internet SCSI, Serial Attached SCSI and
similar concepts - we're already familiar with the words. |
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Privacy
and Security Regulations - How Do they Impact Storage Systems? - article by
ASNP
What are the legal regulations covering the type of
storage system, backup and disaster recovery and encryption mandated for
companies operating in the US?
This article answers those questions
and is a sound starting point for anyone having the duty of care and
responsibility for their corporate data. Because regulations change so quickly
it's worth considering the impact of these best practises on your own
organisation even if you think you are currently outside the scope of these
laws. That will reduce the level of panic when they creep up on you. ...read the article,,
...ASNP profile,
Backup software,
Disk to disk backup,
Optical Storage Libraries,
Tape libraries,
Web based storage | | |
