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SSDs versus PCIe SSDs -what's the difference? |
Another Last
Call for Tape Backup - from Storage Guardian
Editor:- October 28,
2009 - Storage
Guardian has launched a 'Dust-Off Your Tapes'
campaign to promote its
tape to online
backup migration service.
"We've seen tapes stacked in
basements and hidden in dusty storage closets, and it makes you wonder what will
happen when someone needs to restore that information," says Dave Minns,
client services manager at Storage Guardian. "What we're telling
small-business owners, and the resellers and managed service companies that work
with them, is that the time is right to migrate that information from those
dodgy tapes to the safety of
online backup."
History of
Migration from Tape to Disk Backup
Editor's comments:- In the
decade that I relied on tape backup I lost data due to various causes including
- tape snapping due to optical sensor failing to stop rewind, tape submerged by
water, tape chewed up, and data drop-out due to bad media or dirty heads.
In
the 2 decades since I switched away from tape - I've learned that every other
type of backup also has its own peculiar problems and vulnerabilities too. The
key to data survival is diversity in media types and backup software.
Any single critical point can fail - and then fail again.
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.
RDX QuikStor Now 640GB
Editor:- October 27, 2009 -
Tandberg Data
now offers a 640GB model in its
RDX
QuikStor cartridge "10 year data life"
removable disk archive
product line.
This is 28% more than the previous maximum 500GB
capacity model. Tandberg Data has shipped more than 150,000 RDX QuikStor drives
and more than 450,000 compatible cartridges worldwide. disk to disk backup
Editor's
comments:- You may not be impressed by the capacity - but
reliability is more
important than density for backup
applications.
Originally launched in
November 2005 - "RDX
uses a patent-pending error correcting format, which makes the data 1,000x
more recoverable than in a standard
hard drive. This means
that RDX-stored data will be readable even after the cartridge has been archived
and non-operating more than a decade."
In comparison - if you use
standard hard drives for removable disk archiving my own experience is that
50% are unreadable after 4 years and 80% are unusable after 6 years.
SMART Pays Down Long Term Debt Early
Editor:- October
27, 2009 - SMART
today announced it used
$25
million cash to reduce its long-term debt.
Editor's comments:-
I'm not a finance whiz - but this looks to me like the kind of thing a
company does when:-
(a) - it has the cash
(b) - it's pretty
confident it can generate more, and
(c) - it's strengthening its
position for the long term.
Another SPC-1 Record for TMS SSD
Editor:- October
27, 2009 - Texas
Memory Systems today
announced
that its RamSan-620 - (2U
5TB SLC flash SSD, price $220,000 approx) - has achieved a
record
setting SPC-1 result.
It produced 254,994.21 SPC-1 IOPS with
average response time of 0.72mS and at a cost of only $1.13 per SPC-1 IOPS -
which is better than any competing RAID or Flash solution.
"We are delighted that the RamSan-620 has joined our RamSan-400
and RamSan-320 to create a dream team of SSDs that is setting the standard for
performance and value as verified by SPC-1," said Woody Hutsell, President
of Texas Memory Systems. "Our proprietary Zero Quest technology is deployed
across both our DRAM and
Flash products to ensure that our latency remains the best in the market.
This translates into sustained application acceleration and unrivalled value for
our customers."
See also:-
the fastest SSDs
Foremay Enters PCIe SSD Market
Editor:- October 26,
2009 - Foremay
has entered the PCIe SSD
market with its
EC188
Dragon series - which is now sampling and will ship in volume in Q1 2010.
Supporting
both x8 and x16 slots - R/W performance is upto 1.5 GB/s and 1.3 GB/s
respectively. Both MLC and SLC models are available. Capacities range from
128GB to 4TB. Sequential R/W IOPS is up to 90,000/80,000. Random R/W IOPS is
up to 27,000/12,000.
Features available with the EC188 Dragon PCIe
SSD include power outage protection, dual PCIe configuration through a built-in
PCIe RAID controller, and active garbage collection. OS support includes
Windows, Mac OS X, Solaris, Linux, and UNIX.
Editor's comments:-
Foremay is coy about publicly announcing
prices for the new
Dragon models. But the pricing disclosed to me for a terabyte MLC unit looks
competitive - as it has to be.
Intel Offers Tool to Retro-Fix Missing Active Garbage Collection
Editor:-
October 26, 2009 - Intel
joined the growing roster of SSD
companies who have
announced
support for Trim functions.
These benefit
flash SSDs which
don't have internal fast active
garbage collection.
The company recommends users install the firmware update and toolbox, and run
the Trim function daily to ensure best performance.
pureSilicon Unveils New Military SSDs
Editor:-
October 26, 2009 - pureSilicon
says it will start shipping its Renegade R2 Series 2.5" SATA SLC flash
SSDs later this week.
Sequential R/W speeds are 255MB/s and 180MB/s
respectively. IOPS performance is:- 18,000 IOPS random read: (4K) and 1,200
IOPS random write.
The drives are available immediately in a wide range of densities
(4GB, 8GB, 16 GB, 32GB, 64GB, 128GB) in a low profile (9.5mm height)
2.5" form factor
and -40°C to +85°C operating temperature.
256GB, PATA,
1.8", and
encryption versions
will start shipping in Q1 2010.
"pureSilicon is dedicated to providing high-performance, rugged
storage solutions to the defense, military, industrial, and government markets,"
said Jason Breakstone, founder and CEO of pureSilicon. "While many SSD
manufacturers are focusing their efforts on the mass consumer markets,
pureSilicon is committed to designing and delivering technologies that will
provide significant benefits to our customers such as full-disk encryption and
data declassification
methods. Renegade R2 is designed to operate in the harshest conditions."
pureSilicon says the specs it publishes are "steady-state
performance" results. These are achieved by performing proper
preconditioning, which prepares the drive for real-world usage scenarios and
yields realistic performance benchmarks. Other SSD manufacturers claim 'clean'
(new) drive performance specifications on a new drive, and users should expect
to see performance
reductions in real world use as a clean drive settles into its stabilized
(steady) state — once the drive is nearing capacity and is consistently
performing garbage
collection, wear leveling, and bad-block management.
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How adaptive is the SSD
behavior to changes in itself?
The degree to which this passing of
the intelligence can impact behavior in other parts of the SSD - is what I
call adaptive intelligence flow symmetry. |
| 11 Key Symmetries in
SSD design | | |
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Re Foremay, Dragons and
SSDs...
Would users buy an SSD just because it has an animal in the
name?
If so - what animal should it be? |
| animal brands in the
SSD market | | | |
