Transcript
S TO R A G E S W ITZE R LA N D INCREASING VM DENSITY WITH SERVER SIDE CACHING - PROXIMAL DATA BRIEFING REPORT
George Crump, Senior Analyst Increasing the number of virtual machines (VMs) per host
on the potential of server side caching technology that can
is a critical next step in the design of virtualized server
compliment the shared storage infrastructure.
infrastructures so that the growth of virtual hosts does not begin to eat at the original ROI of the virtualization project.
With most solutions there are two components that need
The problem is that the more VMs per host, the more
to be addressed. First there is the need for hardware to
storage I/O each host consumes and eventually the
actually store the data. The good news for data centers is
latency of the storage network and the storage system
that this hardware is now plentiful. There are multiple
becomes a key bottleneck.
categories of server side solid state hardware and there are multiple vendors for each category.
Solid State Disk (SSD) is viewed as the key solution to this problem. Its zero latency nature combined with its raw
The challenge has been in the second component which is
performance is ideally suited to the massive random I/O
the software to actually perform the caching. While there
stream that a host densely packed with VMs can generate.
are a number of software solutions each has potentially
The challenge with SSD is that today it is too expensive to
significant weaknesses. They are either owned by a
place everywhere, so how it is leveraged in the
hardware vendor, which can limit choice or they don't fully
environment is a key decision in the selection process.
support the hypervisor or guest OS that the customer is most concerned about.
Potentially the most surgical of placements would be in the host itself. Using SSD in the server would eliminate
In an effort to change the status quo, Proximal Data has
any network latency and act as a compliment to existing
announced a server side software-based caching solution
shared storage. Caching technology could be used to
that can work with a variety of solid state flash hardware
store a copy of the most actively read data locally in the
solutions including PCIe controllers and SSDs. Proximal
server for instant access while maintaining constancy with
Data's AutoCache solution works at the hypervisor level,
the copy on the shared storage device. As a result
meaning that it does not require a driver in the guest OS.
vendors have been trying to design solutions that deliver
[1]
Native VMware Support
capable of supporting more VMs with existing storage infrastructures without sucking up critical system resources
A key feature of the Proximal Solution is that it does more
or adding more hardware. After purchasing and installing
than just run at the hypervisor level, it coordinates its
the SSD in the server, download the Proximal Data
actions with the hypervisor. AutoCache supports vMotion,
software and install it on the ESXi host (both 4.1 and 5.0
Distributed Resource Manager (DRS), VMware High
are supported).
Availability (HA) and vStorage API for Array Integration (VAAI). AutoCache also shows up a functional management The software configures from a single "vib" and a wizard window within vCenter and vSphere, something that no
walks the administrator through the process. Turn on the
other solution that I know of does today. That means that
auto-cache software and within minutes (thanks to the
cached data is fully in sync with the virtual environment so
write through design) AutoCache should start delivering
that data integrity is maintained.
performance improvement. Finally Proximal Data includes a detailed analytics application that will measure the
AutoCache is a read cache with write through capabilities.
performance improvement and provide guidance as to
This means the most common I/O type, a read, is typically
whether adding more solid state storage will further
going to be accessed from the SSD. New writes are stored
improve performance or not.
on the server SSD but are also sent "through" to the storage system. This means that the recently written data
Storage Swiss Take
does not have to be re-promoted to the cache area. Which, since the most recently written data is the most likely to be
The initial reaction after our analysis of Proximal Data's
retrieved again, should also improve performance and save
AutoCache software was "finally". The parade of cache
the written data from being re-qualified for promotion to
vendors started almost two years ago and even then the
the server side cache. In this case AutoCache already has
virtualization use case seemed obvious. It was surprising to
the data, so it just keeps a copy.
see the limitations of many of these solutions and it is nice to see that vendors are finally closing these gaps.
Another reason that write performance will improve with AutoCache, even though it is a read only system, is
One of the most interesting capabilities of AutoCache is its
because reads are no longer consuming network or
rapid return on investment and simplicity of
storage system bandwidth. The system and infrastructure
implementation. One could start seeing the benefits of SSD
become almost entirely dedicated to write traffic. For
right now. Most data centers have an extra SSD device or
example in a typical 80/20 read to write ratio environment,
space in their servers for a drive. Even with the SSD
potentially 80% of the I/O no longer impacts the storage
premium, buying a basic drive is relatively cost effective.
network or system.
All that would be left is to install the software and see if performance improves. When it does they can then make
The speed at which the AutoCache software can start
the jump to a more robust SSD type, such as a PCIe based
delivering a return on the SSD investment may be the most
SSD, knowing that the investment will live up to its
compelling feature of all. Virtualized systems will be
potential.
About Storage Switzerland Storage Switzerland is an analyst firm focused on the virtualization and storage marketplaces. For more information please visit our web site: http://www.storage-switzerland.com Copyright © 2012 Storage Switzerland, Inc. - All rights reserved
[2]
