1. TECHNICAL BULLETIN / COFFEE BREAK
SOLID STATE DISKS AND
STORAGE TIERING
A NEW DISK TIER
Standard hard disk drives (HDDs) are spinning disks, and their mechanical
actions can create a delay in data retrieval. Solid-state disks (SSDs) are an
exciting improvement in disk technology - made of silicon memory chips and
with no moving parts, SSDs have no rotational delay and near zero seek time,
dramatically reducing response times. SSDs can be extremely valuable to
applications that need fast performance.
SSDs offer a high-performance storage tier commonly
referred to as Tier 0. If storage administrators know
The solid-state disk market
of data that will be in high demand, they can place it
on SSD for fast performance, and place other data on
is growing as automated
HDD tiers. Since the effectiveness of SSD as a disk tier storage tiering takes hold, but
is based solely on how well the administrator can place it remains difficult for IT to
data, it remains a solution that is useful for IT shops with determine which applications
a known performance problem on specific data sets. can benefit from SSD tiers.
Most IT organizations are still unsure of whether SSDs
can help them cost effectively.
THE NEXT EVOLUTION: AUTOMATIC TIERING
Recently, however, storage vendors have begun offering automated tiering along
with better storage controller integration. Arrays can use SSDs dynamically,
in concept like a dramatically larger cache. Instead of fully populating an
enclosure with SSD drives, only a
few SSDs are included; intelligent
load-balancing algorithms identify
“hot” data sets and move them to
the SSD tier. When the data sets are . . . And then
Solid State Disk
no longer “hot,” they are moved back Hot data is returned to HDD
to a slower tier. Organizations can moved to SSD. . . when no longer
hot.
use fewer SSDs, and use them more
efficiently. This type of automated
deployment can spread SSD usage
across more data and applications,
Hard Disk Drives
eliminate the manual task of assigning
data to an SSD tier, and reduce costs.

2. HOW DO I KNOW IF IT’S FOR ME?
Because SSD storage is expensive, organizations want to be sure of its benefits before making
an investment. Solutions that require administrators to manually track and move data offer fewer
SIMPLIFY YOUR STORAGE AT WWW.DELL.COM/PSSERIES
benefits than those that monitor and move data automatically. In addition, it is difficult to know
which workloads need this class of performance, and whether the benefit is worth the cost. Will
SSD implementation improve an application’s performance, or can that application achieve only a
certain performance level no matter what disk type it uses? These answers are hard to ascertain
and often the only way to find out is to try a different disk and see what happens.Knowing your
workload characteristics will help you determine whether SSDs can help - unfortunately, these
characteristics are not easy to distinguish.
IDENTIFYING TIER-ABLE WORKLOADS Best practices designed to alleviate
Automatic load balancing with SSDs can
hotspots may be at cross purposes with
improve performance as long as the active automated storage tiering with SSD, and
data set fits in the SSD storage, but currently may change in the future.
there are no tools in operating systems or
performance and streamline storage costs.
storage arrays to identify active data set size.
Without hotspots, administrators may be
Storage arrays offer performance statistics,
forced to place all of an application’s data on
but that data describes only what happened
high-performance disks to ensure
for an entire LUN. Plus, there is no way to
high performance. With hotspots,
estimate how workload characteristics would
they may configure a small amount of
change on a different storage medium. We
high-performance SSD for some data, and
can see where the storage system is busy, and
less costly HDD and RAID types for the
we can see whether the application is waiting
rest. The growth of SSD in the data center
or not, but we cannot predict how much faster
will alter many best deployment practices.
an application might perform with improved
storage performance. These practicalities will EVALUATING TIERED STORAGE SOLUTIONS
be ironed out over time as the use of these For known tier-able workloads, SSDs are a
technologies matures in operating systems, great advancement. This popular and growing
applications, and storage devices. technology is more widely applicable with
SOME ARE, SOME AREN’T automated storage tiering. When considering
these solutions, be sure you know what you
Since data access hotspots make tiering
are getting. What processes are automated
beneficial, workloads with hotspots are more
- selection of data to move, actual data
appropriate for SSD tiering than those without.
movement, or both? Is data movement only
For example, in virtual desktop infrastructures,
at the LUN level, or can more granular hot
a master image is created from which many
spots be accommodated? Does automated
desktops boot. When many desktops boot
tiering impact or limit other advanced
simultaneously, they work that image very hard
functions such as snapshots and replication,
— this is a naturally tier-able workload that is
and do these data copies automatically
easy to identify because you know how it will
move to the slower, less expensive tiers?
be used. Many databases are also prone to hot
spots.
SSDs offer significant benefits if they fit
SSD TIERS IMPACT APPLICATION your workloads. However, if your workloads
DEVELOPMENT AND DEPLOYMENT do not require high performance or are not
The ability of automated SSD tiers to handle tier-able, an investment in SSD’s may not
data hotspots will impact application be cost-efficient. While your system may
development and deployment. To optimize perform well, it could be over-provisioned and
performance, developers and administrators under utilized for what the applications can
follow best practices designed to minimize leverage. As these technologies mature, more
or avoid hotspot creation. These traditional information should become available to help
best practices may not be appropriate administrators know exactly which data sets
when intelligent, automatic tiering is will benefit from SSDs and automated tiering.
available. Because of automated tiering
and SSDs, hotspots can be used to improve
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