FINAL WORD
We will let you in on a secret: Most hard
disk arrays, which have appeared on the
market in the last five years are actually
hybrid arrays. Provided the active data
inventory and dataset fits into the highspeed flash tier, hybrid arrays can achieve
high performance.
But as soon as the hybrid flash tier is
bypassed or overrun due to an increase
in random access or a change in the
datasets, the performance and more
importantly the latency, will suffer
enormously, because the read-write speed
of hard disks is very slow (in the doubledigit millisecond range).
An all-flash array can sustain high
performance and consistent submillisecond latency in such environments
because there is no tiering layer as all
data is kept on flash storage. The lowest
common denominator to performance
and latency is the all-flash tier.
Flash storage makes the
difference
The performance benefits of flash
storage are already well-known: The
short latency times and the capability
to supply hundreds of thousands
of IOPS ensure that virtual desktop
infrastructures (VDIs) respond
significantly quicker, virtual server
infrastructures (VSIs) can be managed
on a more predictable and simpler basis,
and databases and business analytics
applications can be expedited.
MOHAMMAD DUALEH
Regional Sales Manager,
MENA, Pure Storage
To achieve these performance benefits
and to be more reliable and also more
affordable, than mechanical disk, flash
storage cannot be treated like mechanical
hard disks. Particularly in terms of reliability,
the error behaviour of the two storage
media, for instance, differs completely. If
you examine how flash storage is worn
down with respect to bit error rates, you
can determine the following:
• In the case of hard disks, mechanical
defects are caused by vibration, constant
motion, voltage fluctuations and heat.
Bit errors frequently occur in close
proximity to each other, and multiply
exponentially in proportion to the
capacity and age.
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INTELLIGENTCIO
• In the case of flash storage, bit
errors can be attributed to wear
(program erase cycle). The medium
simply wears out over time. First it is
only possible to read the data, then
comes complete failure. The rate of
uncorrectable bit errors, on the other
hand, remains relatively constant on
hard disks in relation to the number
of writes processes.
In case of flash storage, read processes
are free and write processes expensive
– behaviour which is the opposite of
that on a hard disk. The read and write
processes are largely asymmetrical,
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