|High-Bandwidth, Low-Latency, I/O
This article describes the general development of the storage area
network (SAN) and its derivative, the RAM-SAN. The RAM-SAN
is a SDRAM based SAN element with a greatly reduced latency as
compared to disk based SAN elements. Texas Memory Systems
manufactures a RAM-SAN, called the SAM-500. It has a 64
Gbyte storage capacity, an available aggregate I/O bandwidth of
2.8 GB/sec, and up to 15 Fibre Channel ports. The SAM-500
scales with both storage and I/O bandwidth.
This article describes RAM-SAN applications. A
typical RAM-SAN application is one in which speed is the ultimate
requirement. Whether your SAN has transactional databases, data
warehouses, shared storage, or streaming media and internet caching,
the RAM-SAN can provide the very low latency and high bandwidth
capabilities that you need.
makes for an ideal RAM-SAN.
||The SAM-500/520 systems
have been designed from the ground up to perform as an ideal RAM-SAN.
High bandwidth and very low latency are the main features of
the SAM-500/520. This is
accomplished with the use of a fast access SDRAM based memory.
The SAM-500 has a storage capacity of 32 Gbytes and the SAM-520
has a storage capacity of 64 Gbytes.
Both SAM systems include 15 Fibre Channel I/O ports that
operate at full speed. Each Fibre Channel interface includes special hardware to
reduce latency and speed up access time.
With this awesome capability, the SAM-520 can easily fulfill
all current access requirements and still have a wide margin for
One technique for removing the limitations of disk-based storage is to
replace the disk drives with RAM-SAN - a fast-access synchronous DRAM
(SDRAM) - as the basic storage media. While this method is
costly, it can dramatically improve SAN performance under worst case
conditions. With the RAM-SAN, latency is virtually eliminated
and data access is immediate. The RAM-SAN architecture also
allows for many high-bandwidth I/O ports, each supporting simultaneous
random access. The power of the RAM-SAN is its ability to access
random data quickly and independently of the previous data access.
The RAM-SAN removes the time critical
I/O bottlenecks inherent to RAID-based storage devices. With
SDRAMs, data retrieval is virtually instantaneous. Ultra low
latency performance is maintained (<10 microseconds) across a wide
range of operating scenarios -- accessing short files, long files,
random files, or shared files. Traditional SAN rotation drives get
progressively slower as more computers attempt to access the
SAN. The RAM-SAN gives your computers immediate access even
under maximum load conditions.
While the RAM-SAN only requires a
modest 10.5" of rack space, it still provides more effective
bandwidth (3 Gigabytes/sec.) than refrigerator-sized cabinets of disk
arrays. This available bandwidth provides an easy growth path or
on-demand extra capacity for special requirements. The RAM-SAN
can be expanded to a memory capacity of 64 Gigabytes and an I/O
capability of 15 Fibre Channel ports operating at full speed.
The RAM-SAN delivers 500,000 I/Os per
second to your applications. Store your OLTP database on the
RAM-SAN and you will see instant and dramatic improvements in
application response time. If your ERP system is facing storage
bottlenecks, the RAM-SAN can be used to open up the I/O
floodgates. The RAM-SAN also accelerates database "hot
files" access. Data warehouses with heavy user access,
complex queries, or fast load requirements exhibit screaming
performance improvements with the RAM-SAN.
comes with a standard factory configuration allowing the user to
attach it to their Fibre Channel fabric and have instant access
without requiring any additional configuration. The RAM-SAM connects to an existing network via one or more Fibre
interfaces which attach directly to the ports of a Fibre Channel
switch or to servers providing Fibre Channel connectivity.
Dedicated links may be reserved for demanding workgroups and users,
thus providing the ultimate in SAN performance. Once attached to
the Fibre Channel network, each Fibre Channel HBA driver should
automatically detect the RAM-SAN's presence. The SAM-500 may
then be accessed like any standard storage resource on the network,
only much faster. Each FC-21 connection may be individually
configured to permit unrestricted global memory access or to limit its
permissible access to a subset of the overall system memory.