RAID is
an acronym for
Redundant Array of Inexpensive Disks. |
In the mid 1980's when
this term first entered public awareness, you could buy 2 types of
disk drives, either low
cost drives such as used in the average PC, or high speed high performance
mainframe drives as used by Quantel
in its digital video effects systems.
The huge market for PC disks soon became the leading edge technology
drivers for disk storage and overtook the larger minicomputer and mainframe
form factor disks in speed,
reliability and
capacity.
By the late 1990s RAID systems using PC form factor disks
had become the most common form of bulk storage in enterprise servers and even
some (Unix) mainframes.
Today the original RAID concept remains valid even though hard disks
have changed form factors many times in the past 20 years (8", 5.25",
3.5", 2.5", 1.8" and below 1") and the concept may be useful
in the near future when the "disks" in the array could actually be
flash solid state
disks and not traditional
hard disks.
You
can create a virtual disk array which looks electronically just like a bigger
ordinary disk, by attaching a bunch of disks working in parallel and connected
to a
RAID controller
interface.
The combined system can be programmed to provide desirable
characteristics such as faster data throughput (for example a 4 disk
wide system could have a data throughput capability 4 times faster than a single
disk).
RAID can also provide
fault tolerance, because redundant disks can be added into the array and
the data split up in such a way with redundant error bits that there is no loss
of data if any single disk fails (or if 2 disks fail in some RAID
configurations) - provided the dead disk(s) is replaced and the data rebuilt
before the next failure occurs.
RAID doesn't always result in an
application speedup. It can slow down the access time in some types of
application in which the data sets are small and randomly located - because the
latency of the RAID controller is additional to the disk's own access time. ...from
Megabyte's Storage
Dictionary | |
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| Nibbles Re:
RAID History |
IBM received the first patent
for a disk array subsystem in
1978, and
co-sponsored the research by the University of California at Berkeley that led
to the initial definition of RAID levels in 1987.
IBM launched the
first modern style RAID systems in
1990
It wasn't until the late 1990's that RAID technology became a "must-have"
building block in commercial Unix servers.
In the future RAID
technology will be already integrated in most home PC's and entertainment
systems, because home users don't do backups, but they will have large digital
entertainment libraries which won't fit neatly onto a single disk. | |
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Nibble:- RAID and Me
I first came
across the concept of RAID in 1986 when I joined a company called Databasix
as their hardware engineering manager.
Databasix, based in Newbury
in the UK, was founded by John Golding from the nucleus of an earlier company
he had been in called Microconsultants.
Microconsultants had spawned
rich sister company Quantel.
Peter Michael, who had been the business and technical brains in both these
earlier companies, gave Databasix a very generous start in life from what I
could see by the pool of talented people and money which had mostly been already
spent when I joined the 70 people or so in the new "start-up".
Among
the many things on my to-do list was to build a working RAID controller and RAID
array demonstration system.
"I don't know much about hard drives"
- I said. I could afford to be honest - because these guys had already seen the
worst when they first met me. My VC backed networked data acquisition company
was going bust and they had been a potential buyer.
"There's not
much too it." My boss said. "Just read the manuals that come with the
disk drives. We want to see if RAID will give us fast real-time disks at a cost
that's significantly less than the video disks from Japan used by our sister
company Quantel."
"OK" I said. "I don't know much
about RAID either."
"Nobody does. Here's a bunch of
articles. They tell you all you need to know. We'd like the demonstration ready
in 3 weeks."
"That sounds like a very short time to me."
"We've
already ordered the disks to save time. You order whatever chips you need, and
use some of the software guys to help on this."
From memory, I
think I got the demo deadline pushed out to about 4 to 5 weeks.
We
also had an Artificial Intelligence demo being worked on at the same time by
about 50 software engineers, and a parallel computing demo, but the RAID
functionality was the "must have" thing which could not be easily
dropped from the sales plan.
We did build a working 4 drive RAID
system. One of our biggest problems had been the high rate of Dead On Arrival
disk drives. That caused a lot of problems which we initially blamed on the
software. Hard drives were a lot more sensitive in those days and could be
killed just by putting them down on your desk.
But by then I knew a
lot more about disks and realised that the Inexpensive Disks we used in our
demonstrator weren't anywhere near as fast as they could have been, because they
were the wrong standard. Then, as now, there were many interface standards for
disk drives. If you're going to build a fast system then you might as well use
fast building blocks. Dataquest was telling me that we should probably be using
SCSI instead.
As my imposed wish lists started to pile up and
commercial reality started hitting my new employer, I decided that it would be a
heck of lot easier to partner with a disk controller company which was already
down this part of the curve, and later we became a beta site for dozens of
manufacturers of processor cards, array processors, hardware interfaces, memory
and disk drives as we tried to make a business out of selling the technology
curve to military buyers almost before it was really there. That was great fun,
but a different story.
It was about 10 years after that before RAID
systems next appeared in my life - when RAID companies like DEC (acquired by
Compaq and now part of HP) and Data General (acquired by EMC) started promoting
their RAID systems to readers of my Sun foused
SPARC Directory.
Nearly 12 years after my first acquaintance with RAID it became one
of the first 4 product categories here on STORAGEsearch.com. And although the
interface patterns have changed over the years, from DAS SCSI, then
Fibre-channel SAN, then Ethernet NAS, and then iSCSI, the ideas inside the box
have remained the same.
When you get to be an old guy like me, it's a
lot easier if some of the new stuff which hits your brain, is actually a rehash
of old stuff.
...more about Databasix.
I didn't want to interrupt
the narrative flow above - but the core Directors at Databasix when I joined
were:- John Golding, Andrew Bruce, Ray Potter and Dan Boxshall.
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RAID news |
Anticipating demise of RAID
controller market...
LSI will Compete with Fusion-io
Editor:-
January 26, 2010 - LSI
and Seagate
today
announced
they have collaborated on designing
PCIe SSDs for the
enterprise accelerator market which will sample in Q2 2010.
Editor's
comments:- LSI approximately the 163rd company to enter the
SSD market (not counting
SSD SoC makers - which
would push the score to about 185).
Partly LSI's move is due to a
strong suction effect from the
SSD market bubble -
and partly an inevitable step given that the high end of the
RAID controller market
is going to disappear.
There's little point in spending money aggregating
IOPS in an
array of hard disks -
if the result costs more, is slower and is less
reliable to
operate.
In Q4 2009 - PCIe was the #1 most popular form factor
for SSD related searches. (Higher than than for
2.5" SSDs.) In
the same quarter the single most popular company profile viewed by readers
was PCIe SSD evangelist
Fusion-io. Dozens of
oems have already entered this market - thereby preparing the educational
framework for user acceptance of this technology.
New edition - the Top 10 SSD Companies
Editor:-
January 7, 2010 - StorageSearch.com
today published the 11 quarterly edition of the
top 10 SSD oems -
ranked by search volume in the 4th quarter of 2009.
This is always
one of the most popular articles on our site. I know that many SSD companies
themselves are nervous and eager to see how they've fared in this important list
which predicts future winners in the market based on the world's leading SSD
focus group. I've tried to be more direct with my own analytical comments too -
even if it means repeating some things I've already said in other places -
because I know that most of you don't have the time to read hundreds of SSD
articles. ...read the
article
EMC Casts SSD Divining Rod into Hard Disk Arrays
Editor:-
December 8, 2009 - EMC
today published a report on its new
fully
automated storage tiering concept which the company says will simplify user
operations needed to optimize storage allocation between
hard drives and
SSDs within the company's
arrays.
The company says some of this functionality is
now
available on some models.
Editor's comments:- although
better than nothing - adding a software manager retrospectively to storage
arrays which were never designed for SSDs in the 1st place can never deliver as
much performance as a true native
ASAP
SSD appliance (where some of the support is built into the hardware) - and
nowhere near as much performance as the
fastest SSDs (EMC
has never been in this list) when optimized by human SSD hot shots.
In
order to get the full benefits of the SSD acceleration paradigm EMC will need to
dump its legacy storage array designs and start offering boxes which have been
designed from the outset to support large amounts of
PCIe SSD capacity.
Without that - its systems will remain moderate performers at immoderate
prices.
To put it another way - bolting SSD tiering onto controllers
designed for hard drives is like trying to do air traffic control by having a
traffic cop standing on the ground and waving his stick. You can make the stick
a brighter color and give the pilot stronger glasses - but it's not going to
give you the traffic movements you get from integrated avionics.
Error Correction in MLC Flash SSD RAID
Editor:-
October 28, 2009 - ECC
Technologies has published a new article which examines
data reliability
issues in RAID systems using MLC flash.
In his survey of
RAID and error correction
related to SSDs the author
Phil White said he thinks that "MLC NAND Flash memories should
implement nonbinary error-correcting codes such as a Reed-Solomon (RS) codes so
that all of the bits from one cell are in one symbol. The communications
industry has been doing that for decades, but the Flash industry has been
implementing a scheme that forces the bits from one cell to be in separate
records (pages) so that one cell failure can cause multiple binary symbol
failures – which seems illogical."
I asked him to expand on
this for our readers.
In reply - Phil said he doesn't think that
most NAND Flash (SSD) companies have a high level of expertise in the field of
error-correcting codes.
"Many of the
NAND Flash controllers
that are out in the market now have ECC Tek's ECC designs in them. None of the
controller companies who have come to us have any idea how to implement binary
BCH encoders and decoders in hardware. I doubt if any of the Flash
manufacturers have that expertise either."
"For years the
Flash manufacturers implemented a simple binary scheme that corrected only 1 bit
in a page. I don't have evidence to prove this, but I believe the NAND Flash
manufacturers simply decided to extend their original scheme to correct N bits
in instead of 1 bit to handle higher error rate devices. I also believe that
they implemented a scheme for MLC NAND Flash to "randomize" the errors
when a cell fails.
"Consider 4-bits/cell. When a cell fails,
0-4 bits may be in error. In order to keep using binary error-correcting codes
that only correct bits, they designed the chips so that all of the bits from
that cell are in different pages.
"To the best of my knowledge, they never considered using RS
codes so that all of the bits from one cell are in one RS symbol. For example,
assume a RS code with 12-bit symbols. Each RS symbol can hold the data from
three 4-bit cells, and if those three cells happen to fail, it will only corrupt
one RS symbol. RS codes can correct t "symbol" errors and s "symbol"
erasures as long as 2t+s is less than or equal to R where R is the number of "symbols"
of redundancy. The most natural and powerful thing to do is to put all of the
bits from one cell in one RS symbol." ...read the article
See
also:- Data
Integrity Challenges in flash SSD Design - a recently published article by
SandForce.
Fusion-io Ousts SAS HDD RAID at MySpace
Editor:-
October 13, 2009 - Fusion-io
published a
case
study showing how their ioDrive
SSDs helped MySpace reduce
servers, claim back 50% rack space while increasing application performance and
massively decreasing electrical power.
The ioDrives performed much
better than the legacy SAS
disk arrays, but more importantly for MySpace, they did it with much less
hardware. A single ioDrive allowed MySpace to replace a 2U HP DL380 server with
1U HP DL160 server.
In the initial phase of this deployment MySpace
replaced 150 of their standard load servers, recovering 150U of rack space.
Additionally, the ioDrives' phenomenal performance reduced its need for heavy
load servers, allowing it to permanently end-of-life 50 of 80 heavy load
servers. This allowed it to recover another 65U of rack space.
Reliability also
increased and the Fusion-io solution is
greener.
Estimates suggest that the power savings alone could easily pay for the
ioDrives over their lifetime.
MySpace says it plans to replace
another 1,770 2U servers with Fusion-io enabled servers as they reach their
end-of-life. ...read the
article (pdf)
Editor's comments:- If you ever wondered why
there are so few companies making
SAS SSDs - this is one
of the reasons. And it's also why search volume for
PCIe SSDs is now
higher than that for 2.5"
SSDs.
Accusys Announces New iSCSI RAID
Editor:- October
12, 2009 - Accusys
today announced a
new range of
rackmount IP SAN products.
Accusys iSCSI ExaRAID family
includes 2U-12 bay, 3U-16 bay and 4U-24 bay
RAID systems designed
with active-active redundant controller support for high reliability and
availability, link aggregation and jumbo frame support for maximizing bandwidth
and performance over the Ethernet.
RAID Systems Get 2TB WD Drives
Editor:- September 1,
2009 - Dot Hill
and Pillar Data Systems
are in the 1st wave of companies who have recently started volume
shipments of RAID systems using 3.5" 2TB 7,200 RPM hard drives from Western Digital.
The
new drives were announced in
April 2009.
PhotoFast RAIDs CFast SSDs
Editor:- August 5, 2009 -
PhotoFast
disclosed details of its
G-Monster
Quad Drive SSD which includes 4x RAIDed CFast SSDs in a SATA compatible
100mm x 70mm x 9.5mm module.
Adaptec Ships Flash Cache Backup for RAID Controllers
Editor:-
June 24, 2009 - Adaptec
today announced the availability of
flash
backup options for its SATA/SAS
RAID controllers.
Adaptec's
Zero-Maintenance Cache Protection protects data stored in controller cache for
up to 10 years with no installation, monitoring, maintenance, disposal or
replacement costs unlike lithium batteries.
Editor's comments:-
the industry's 1st flash cache backup module for RAID controllers was
announced in February
2009 by Viking
Modular Solutions.
RAISE Joins RAID lexicon
Editor:- April 15, 2009 -
this week SandForce
has added a new word to the rich RAID lexicon with their new word - RAISE
(which stands for - Redundant Array of Independent Silicon Elements).
RAISE
is the label for the RAID-like protection scheme which their
SSD controller uses
inside 1.8"
and 2.5" flash
SSDs.
Although the word is new, the concept is not.
Manufacturers
such as Texas Memory
Systems, Violin Memory
and Fusion-io have
used similar schemes inside their
rackmount SSDs
and PCIe SSDs for some
time.
LSI Acquires 3ware RAID Adapter Line
Editor:- April
6, 2009 - LSI
today
announced
that it has signed a definitive agreement to acquire the assets and certain
associated intellectual property of the 3ware
RAID adapter business
of AMCC for
approximately $20 million in cash.
Editor's comments:- There are
nearly 500 storage
acquisitions and mergers listed on StorageSearch.com.
Here are some others, previously acquired by LSI.
- Agere Systems (merger) - storage controllers / adapters
- AMI's RAID business
- Infineon's HDD Chip Business
- Mylex - RAID adapters
- IntraServer Technology - SCSI & Ethernet HBAs
- SiliconStor - SATA chips
- StoreAge - SAN systems
IDC Calculates the Cost of Owning Storage
FRAMINGHAM, Mass.
- March 16, 2009 - IDC estimates the total annual cost to "manage"
the world's installed base of external storage is about 60% of all
enterprise storage-related spending, including software, power, cooling,
administration personnel, and services.
"As the industry attempts to control IT costs, specifically
related to storage, IDC realizes that power and cooling costs are not
the only costs associated with external storage," said David Reinsel, group
vp for IDC Storage and Semiconductors research. "In fact, in the grand
scheme of things, the cost to power and cool external storage pales in
comparison with the cost to acquire and manage storage, including the costs for
storage software and storage administrators."
While interest
around storage efficiency technologies (e.g.,
deduplication,
compression, and thin provisioning) has intensified, impacting power and cooling
costs in the longer term, penetration of these technologies is very low. ...IDC profile,
storage analysts
Editor's
comments:- in the past 10 years - the relative cost of owning data
(compared to buying it) has only improved by 20% - as you can see by comparing
IDC's ratios for 2009 - with those published in
1999
- in an article written by Overland Data.
Seanodes Seeks Beta Sites for Clustered iSCSI SAN Software
Boston, Mass. - March 10,
2009 - Seanodes today announced a Beta version of its Exanodes
software for Microsoft Windows Server 2008, enabling these users to repurpose
commoditized or existing hardware as an iSCSI SAN.
Exanodes allows fast rebuilds thanks to an intelligent,
innovative approach that distributes the RAID set across multiple network nodes
and minimizes the risk of a second disk failure during the rebuild window. ...Seanodes profile,
SAN software ISVs,
iSCSI
Winchester Systems Unveils Rugged Rackmount SSD RAID
Editor:-
March 5, 2009 - Winchester
Systems says its will launch a range of rugged rackmount SSDs next week
at FOSE
.
Among the new products is a 1U RAID 5 / 6 protected rugged
SSD array - the RX-1300
FlashDisk - which houses 12x
2.5" SSDs.
Interface options for the array include
SAS,
FC and
PCIe.
"Customers
find that they need field deployable storage and servers that exceed standard
commercial capabilities but not full military rugged specifications or prices,"
explained Mr. Joel Leider, the company's CEO. "Our rugged storage and
servers provide extra security and protection against dust, rain, shock and
vibration at COTS prices which are about half of full military standard costs."
The US Army has approved these units for field use. They are deployed
in harsh environments worldwide in HUMVEEs and stationary shelters. FlashDisk
RX disk arrays feature RAID 6 dual parity so even if 2 disk drives fail or
become unreadable, the data will remain intact. See also:- rackmount SSDs,
Military & Rugged
Storage.
Accordance Launches 1U Compact RAID
Des Moines, IA -
February 24, 2009 - Accordance Systems today announced availability
of its new ARAID M200 RAID 1 Controller.
The 1U high M200 behaves
just like a single high reliability 7,200 RPM SATA
hard disk which
constantly mirrors data onto 2 internal hard drives assuring that your system
is protected in the event a drive should fail. Replacing the failed drive is
easy with the ARAID sliding drive trays and can be done while the system is
running. All BIOS and operating systems view the ARAID 2200 as a simple drive
and treat it accordingly. There is no need for drivers or any other
applications.
All ARAID processing is handled on the ARAID device
controller independent of the computer's main processor. Most onboard
RAID and PCI RAID tax
cycles from the motherboard CPU. ARAID creates a RAID 1 array on the fly from
an existing drive, with no danger of losing data. Contrast this with typical
RAID controllers that
require the user to destroy, and then create an array from scratch. Typical
RAID 1 solutions are not considered to be a backup solution. While data is
replicated, it is not safe from viruses, spyware, etc. An ARAID is different
because you can remove a drive from the unit and replace it with another drive
within seconds.
The removed drive can be treated as a
backup and taken off-site
for secure storage. The ARAID recognizes the new drive and immediately begins
to mirror all data to it. Most ARAID users buy 1 to 7 spare trays and rotate
backups offsite in a similar manner as
tape. ...Accordance profile
Viking Launches SSD Backup Module for RAID Cache
Foothill Ranch.
Calif. - February 18, 2009 - Viking Modular Solutions announced
ArxCis-NV - a flash SSD based backup for cache memory in RAID controllers.
"Current
technology of backing DRAM modules with batteries provides protection for
approximately 72 hours and also brings a host of battery related issues to IT
managers. ArxCis-NV products help eliminate these issues..." said Adrian
Proctor, VP of Marketing for Viking Modular Solutions.
The ArxCis-NV is a JEDEC edge compatible registered DRAM module
with ECC which can write to its associated embedded SSD at 80MB/s triggered
by a drop in rail power. The module hold-up power (typically 10 to 15 seconds,
depending upon DRAM density) is supplied by Supercapacitors, which only require
10 seconds to fully charge. ...Viking profile,
RAID controllers
RAID Inc Launches 1U Rackmount SSD
Methuen, MA - January 27, 2009 -
RAID Inc. announced the availability of its new 1U SSD RAID.
The Razor SSD
is a 12 bay 4 port fibre-channel
system using COTS 2.5"
SAS SSDs in a
RAID protected array. The
Razor comes with RAID's patent pending
StorageWatch service -
which proactively monitors storage conditions in real-time. ...RAID Inc profile,
rackmount SSDs
RAED Demo at CES Aims at Gamers
Editor:-
January 6, 2009 -
Advanced Media, Inc. demonstrated a RAED configuration of its
flash SSDs today at CES.
This shows the kind of
performance that gamers can get from upgrading their PCs. Using 4x Ultra-S Plus
MLC SSDs in RAID 0 the demo delivered throughput as follows:- 450MB/s read and
330MB/s write.
The performance is unremarkable for a flash SSD array. All
rackmount SSD
systems are already much
faster. So you may
be wondering - why did I mention this at all? And is the appearance of the word
"RAED" above a typo?
Well consider this. When the term
RAID was coined in the
1980s - the letter "I" stood for "inexpensive". At that time
the idea was that you could use a bunch of inexpensive PC hard disks (which were
then 5.25") to deliver the same throughput as physically larger server
drives (which were 8.5" and even much bigger). The media whizzed past the
heads at a higher linear speed on those big diameter disks - even at the same
RPM - and there was plenty of space to pack in a crowd of heads.
That
was 20 years ago and things change. Now all
hard drives are "inexpensive"
- and at the same spin speed there's no performance difference between a server
drive and a fast PC drive. If you want faster throughput you have to use COTS
flash SSDs in the array - instead of HDDs - because the rotational roadmap long
ago hit
its limit. Many vendors have been doing this for a year or more now,
examples include EasyCo,
EMC and
Superior Data
Solutions .
This is where the "E" comes in. "E"
for "Expensive" - because it's mostly true that for the same capacity
an SSD costs more than an HDD. Hence we get RAID = Redundant Array of
Expensive (solid state) Drives. And thus another useless acronym is born. Will
my RAED term be adopted by vendors to usefully differentiate their SSD based
arrays? Or will it join the pantheon of lost RAID jargon such as RAIN, RAIGE,
SAID... ...Advanced
Media profile
G-Tech Launches Desktop SSD RAID for Macs
Macworld, San
Francisco - January 5, 2009 - G-Technology today announced a new
family of external drives based on 2.5" SSD technology.
The
G-DRIVE mini SSD has a FireWire and USB interface and costs $599 for 120GB and
$1,299 for 250GB.
The G-RAID mini SSD has
eSATA,
FireWire and
USB interfaces and upto
195MB/sec data transfer rates. Price is $2,199 for 500GB. ...G-Tech profile
A-DATA Announces 3.5" SSD RAID Enclosure
Taipei, Taiwan -
December 30, 2008 - A-DATA Technology Co., Ltd siad it will ship a
3.5" SSD RAID enclosure in Q1 2009.
The A-DATA XPG Dual SSD 3.5" RAID Enclosure is a complete
RAID solution through the
use of 2x 2.5"
SATA SSDs mounted on one
standard 3.5" form
factor drive cage. This multifunctional RAID enclosure can be used as 2
separate drives, as a redundant drive to protect against drive failure, combined
to become one high-performance drive or combined to become one large drive. All
these different RAID configurations and more can be set by using a hardware DIP
switch on the back of the unit or software. Connection via
SATA or
USB enables easy direct
access.
...A-DATA profile
Infortrend Reduces RAID Performance Hit from Failed Data Links
SAN
JOSE, Calif. - December 2, 2008 - Infortrend today announced a new
technology - "Dynamic Logical Drive Assignment" which boosts R/W
performance in dual-controller RAID subsystems when a data path has failed.
Typically, failed data links lead to performance degradation because the storage
controller has to re-direct the I/Os targeting the logical drive whose primary
data path is broken. Infortrend now supplies all its EonStor dual-controller
arrays with the "Dynamic LD Assignment" technology to improve
performance by eliminating the re-rerouting overhead. Once the failure is
identified and corrected, optimal system performance can be immediately
restored. The "Dynamic LD Assignment" now comes with all EonStor
Fibre-,
SAS-, and
iSCSI-host
redundant-controller models using Firmware ver.3.64J or later.
...Infortrend
profile, RAID systems
Condre Markets APPLE Video Optimized RAID
Minneapolis, MN -
November 5 , 2008 - Condre Storage, Inc. is selling a new APPLE
optimized AV RAID - the Bullet.
Built on proven technology with a
4Gb Fibre Channel front
end and SAS/SATA drives. The Bullet AV RAID scales up to 64TB capacity and is
capable of up to 3 streams of (10 bit), 1080, Uncompressed HD video. MSRP is
$11,999 for 12TB of Fibre Channel to SATA storage which includes 1 year next
business day on site support.
"Condre Storage is excited by this unique offering for the
APPLE video market. The
Bullet is an incredibly fast RAID,
and with 2 boxes striped together we've done over 8 streams of 10 bit, 1080/HD
video", according to Condre Storage President Denny Maetzold.
...Condre Storage
profile, Storage VARs,
Video
- editor mentions on StorageSearch.com | |
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| RAID, XAID,
RAIX etc - RAID's Many Aliases |
The long established
word "RAID" has been stretched by marketers into many other
disguises to make their products sound better.
The RAID system concept
itself is simple, being a box of disk drives with self healing properties which
can be run in parallel for faster data throughput. But that's not sexy enough
for most storage product marketers. So we now have the following refinements.
- RAID connected by SCSI, Firewire or IDE can be called a
DAS (Directly Attached Storage). The RAID has to be connected by
something, but "DAS" sounds more modern, and indicates that you chose
this method of connection in preference to all the others.
- RAID connected by Fibre-channel can be called a SAN (Storage Area
Network). That sounds better already.
- RAID connected by Ethernet can be called a NAS (Network Attached
Storage). Latterly the term IP-SAN has been used to add new freshness to
this word-washing.
- RAID connected by both Fibre-channel and Ethernet can be called a NUS
(Network Unified Storage).
- Even better than plain old vanilla NUS,apparently, is
SUS, or Scalable Unified Storage, coined by the short lived startup
Broadband Storage
- More likely to endure than either NUS or SUS, is market research company
Gartner's term FAS
for Fabric Attached Storage which also lumps NAS and SAN together.
- RAIN (Redundant Array of Independent Nodes) is an
Adaptec creation
- MAID (Massive Array of Idle Disks) is a whimsical term from
COPAN Systems used for
disk to disk backup systems.
- RAIGE - (RAID Across Independent Gigabit
Ethernet) is a creation of Pivot3
although some of concepts sound similar to how
Google implements its
internal storage infrastructure.
- RAISE - (Redundant Array of Independent Silicon Elements) is a
term invented by SandForce.
Their SSD controller uses this protection scheme inside
1.8" and
2.5" SSDs.
- DVRAID - is a proprietary RAID technology from
ATTO Technology that is "optimized
for digital content creation environments that require protection in the event
of a disk failure without the performance penalty traditionally seen with parity
RAID."
- SAID - Self-maintaining Array of Identical Disks - a possibly
overambitious term from Atrato
- RAIDn
- is an algorithm launched in 2003 by InoStor. It never achieved wide
currency.
- Finally, a RAID not connected to anything at all
can be called a
LUS (Lonely Unloved Storage)...
No, I just made this one up.
But you can see the basic principle at work here. And no doubt there will be
other terms later for RAID connected by the Internet or Infiniband. See also:- Megabyte's
Storage Glossary which
includes definitions of the many other strange terms which appear from time to
time in these pages. | |
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