In this issue of Horse
Sense:
-Things we thought you
should know
-The Importance of
Backup
-The Importance of
IOPS
Here
are some things we thought you should
know:
-On 1/1/2012, HP raised prices on some
of its toners 10-17%. Lexmark also
increased supply prices 3-7%. They say
these increases are due to global
economic conditions, currency
volatility, product supply costs, and
transportation costs.
-Following the massive increases and
availability issues due to the floods in
Thailand, hard drive makers Seagate and
Western Digital are lowering the
warranties on their drives 1/1/2012.
Most Seagate desktop drives will go from
a 2 year to a 1 year warranty, and most
enterprise drives and some high
performance desktop drives will go from
a 5 year to a 3 year warranty. Only
Western Digital's Blue and Green series
desktop drives will drop from 3 to 2
years, while performance and enterprise
drives will continue to have a 5 year
warranty. Hard drive allocations are
expected to continue for at least 6 more
months.
-Solid State Drive (SSD) pricing at the
end of 2011 reached $1/GB retail pricing
for some drives. SSDs have been selling
well due to the increases in price and
shortages of traditional hard drives.
-At the end of 2010, according to Intel:
247 billion e mails were sent each day
and 70-90% of them were spam.
There were 1 million computers sold per
day, and the majority of them were
portable.
There were 2 billion videos seen on
YouTube alone in a day.
There were 2.5 billion photos placed on
FaceBook alone in a day.
-Cell phone bandwidth is quite limited
when compared to cable or fiber
connections to your house. Now that
people are downloading books to their
electronic readers and, much worse,
trying to watch video on their phones
and tablets via their cellular
connections, there is a real shortage of
bandwidth. To combat that, cell phone
companies are curtailing unlimited
bandwidth plans, deliberately slowing
connections after a certain amount of
data has been received, charging more
for "premium" service, and other tactics
to limit the overall impact on their
network. A single movie played on a
tablet could consume enough bandwidth
for hours that other people might not be
able to do anything else. If you are old
enough, you might remember a similar
situation played out with dial up access
to the Internet many years ago. Phone
companies found themselves short of
capacity when systems designed for 2
minute average voice calls were faced
with modem users camping on those same
lines for 2 hours.
The
Importance of Backup (Statistics from
Intel)
-It costs $8000 per megabit to
regenerate data from scratch.
-It takes 19 man days to reenter 20MB of
sales data.
-60% of small businesses suffering a
catastrophic data loss are out of
business within 6 months.
The
Importance of IOPS
You are going to start seeing the term
IOPS more often. I have written a number
of articles in Horse Sense that
discussed latency and why it is so
important in computing (in Google,
search for "latency site:
www.ih-online.com "
to see the most recent ones). IOPS is an
abbreviation for Input/Output operations
Per Second. IOPS is a measure of how
much work you can do during one second
and is inversely related to latency. For
example, to read 4KB of data may take 1
millisecond, which gives you 1,000 IOPS.
Unfortunately, standard magnetic hard
disks are not that responsive. They tend
to top out at less than 200 IOPS. This
is because there is a lot of physical
movement involved in reading or writing
from a hard disk and that takes time.
Lower end Solid State Drives (SSDs) on
the other hand, typically exceed 20,000
IOPS. Enterprise SSDs and SSD arrays can
hit 2 million IOPS or more (
http://www.storagesearch.com/ssd-fastest.html).
High end hard disks can transfer data at
up to 145MB/s, but a single low end SSD
can exceed 550MB/s. In addition, typical
SSDs use 2 to 50 times less power,
depending on whether you are comparing
idle or working drives. SSD equipped
devices run without drive noise and
often without fan noise because extra
air cooling is not needed. An SSD has a
shock resistance that is 5 to 50 times
better than a standard hard drive. You
can hit an SSD with a baseball bat and
as long as you don't break any of the
connections, it will still function!
But IOPS and SSDs sound esoteric. Why
should you care about them? IOPS is a
standardized measure of how much work
you can do in a given amount of time. If
you need to do less than 200 IOPS of
work, then it does not matter whether
you are using an SSD or a traditional
hard drive. Modern multi-core processors
are capable of doing much more work, so
your storage system can act like a
really large rock behind your car. When
would you need more than 200 IOPS? It
turns out that it happens more often
than you think. IOPS becomes critically
important any time you are doing work
that causes you to perform lots of read
or write operations in a fairly random
fashion. Reading large directories in
Windows, indexing files for search
purposes, scanning files for viruses,
searching for a particular e mail,
compacting e mail folders, working with
a database, booting your system,
shutting down your system, having your
system go into hibernation or resume
from hibernation, and other tasks
trigger a huge number of reads and/or
writes. Even "normal" tasks can be
taxing if your disk is fragmented.
Reconstructing the pieces of fragmented
files requires that the read/write heads
of a traditional hard disk reposition
lots of times. It looks literally like
the arm of a record player moving back
and forth across a record. Needless
moving of the head across a fragmented
hard disk compromises both performance
and longevity and is why I recommend
disk defragmentation programs. While
files on SSDs can become fragmented, the
time needed to access the pieces is
minimized, so fragmentation issues do
not disappear, but they become less of
an issue.
Perhaps an even more common case where
more IOPS are needed is when a user is
multitasking. If you have multiple
windows open at the same time doing
different things, and if those things
require access to the disk, they are
competing against one another. Data for
those tasks may be scattered all over
the disk. Though your multi-core
processor may be able to handle multiple
tasks at once, if your storage system
cannot deal with the requests for
information, those extra cores are
wasted. In modern computing, the
responsiveness of your storage system
plays a huge role in how well the system
responds as a whole. Where IOPS becomes
critically important is on servers,
especially those with larger databases.
You would naturally expect different
users to need different information. So,
it is like multiplying the single user
multitasking case by each user. On
servers, you can run out of IOPS
quickly. To combat this problem,
database vendors have recommended that
high performance databases be spread
across a large number of conventional
hard disks in a RAID array to provide
the needed number of IOPS for the
organization. A single SSD can replace
multiple hard drives and provide the
needed IOPS in this case with far less
cost and complexity. A fairly readable
article on this can be found here (just
ignore the application specific stuff):
<
http://www.symantec.com/connect/articles/getting-hang-iops?om_ext_cid=biz_con_email_2011_apr_05_news_iops>
A lowly desktop user can easily see a
difference when using SSDs versus hard
disks. Operations involving disk access
will happen more quickly. The computer
will be more responsive. It will not
seem to freeze or think as often because
it is waiting for the disk to respond.
Tasks will continue smoothly. For
example, hard disk backups or copies of
directories will often stutter with
conventional hard disks as the disk
finds something else to back up. This
will not happen with SSDs. You can even
see this happen on a network by watching
how bandwidth is used. An SSD trying to
fill that network pipe will do so
whereas a hard disk will have a spiky
looking graph indicating drops in
transfer rates and take longer. Laptops
run cooler and longer because SSDs take
less power, and adding an SSD to a
laptop is especially noticeable as they
tend to use hard disks that spin slower
and/or stop spinning when unused to save
on energy and noise. The effect is so
dramatic, that when I bought a new
laptop for my wife and son to use this
Christmas, they refused to use it until
I installed an SSD.
With the rise in hard disk prices and
the drop in SSD prices, we should no
longer consider them esoteric or for the
high end. In fact, with the productivity
gains that can be realized by tying SSDs
to modern multi-core processors, at
least one of your drives in your next PC
should be a solid state drive. In fact,
you should seriously consider replacing
or augmenting the conventional hard
drive in your current PC to speed it up
and extend its useful life. And,
although caching solutions and hybrid
drives do exist and have their place, I
submit that only the higher cost per
gigabyte of SSDs is keeping everyone
from adopting them wholesale. If your
storage needs are fairly minimal, and
most desktops and laptops do not need a
lot of storage, solid state is the way
to go. If you need lots of IOPS or high
throughput, solid state is the way to go
as well. Only if you need massive
amounts of inexpensive storage should
you really keep looking at traditional
hard drives.
©2012 Tony
Stirk, Iron Horse tstirk@ih-online.com