IBM X3620 M3 - Manual (Page 6)

A cost-optimized storage-rich alternative to traditional enterprise 2U dual-socket servers
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The 5500 and 5600 Series processors support single-, dual-, and quad-rank memory. A memory
rank is simply a segment of memory that is addressed by a specific address bit.
• A typical memory DIMM description is 4GB 2Rx4 DIMM
• The 2R designator is the rank count for this particular DIMM (2R = dual-rank)
• The x4 designator is the data width of the rank
It is important to ensure that DIMMs with the appropriate number of ranks are populated in each
channel for optimal performance. Whenever possible,
use dual-rank DIMMs in the system. Dual-
rank DIMMs offer better interleaving and hence better performance than single-rank DIMMs. For
instance, a system populated with six 2GB dual-rank DIMMs outperforms a system populated
with six 2GB single-rank DIMMs by
7% for SPECjbb2005. Dual-rank DIMMs are also better than
quad-rank DIMMs because quad-rank DIMMs will cause the memory speed to be down-
clocked.
Another important guideline is to populate equivalent ranks per channel. For instance, mixing
one single-rank DIMM and one dual-rank DIMM in a channel should be avoided.
Notes: It is important to populate all three memory channels in each processor. The relative
memory bandwidth decreases as the number of channels populated decreases. This is because
the bandwidth of all the memory channels is utilized to support the capability of the processor.
So, as the channels are decreased, the burden to support the requisite bandwidth is increased on
the remaining channels, causing them to become a bottleneck. If 1.5V and 1.35V DIMMs are
mixed, all DIMMs will run at 1.5V.
In addition to Chipkill error correction, the x3620 M3 offers an additional level of IBM Active
Memory protection:
memory mirroring.
Memory mirroring works much like disk mirroring. The total memory is divided into three
channels: a primary channel, a backup channel, and an unused channel. Data is written
concurrently to both the primary and backup channels. If a DIMM fails in one of the DIMMs in the
primary channel, it is instantly disabled and the mirrored memory in the backup channel becomes
active (primary) until the failing DIMM is replaced. One-third of total memory is available for use
at any one time with mirroring enabled. (Note: Due to the double writes to memory, performance
is affected.) Because the third channel is disabled with mirroring active, there is no point in
populating it with memory.
Mirroring is handled at the hardware level; no operating system support is required.
DDR3 memory is currently available in 1GB, 2GB, 4GB and 8GB RDIMMs. DIMMs can be
installed individually (not in pairs). However, for performance reasons, in a 2-processor system,
it’s best to install a DIMM per processor.
Maximum memory capacity and speed in 2-processor configurations include:
Memory
Frequency
DIMMs per
Channel
Max. Memory
Capacity
5600 Series 5500 Series
1333MHz
1
(6 DIMMs)
48GB RDIMM
X5650, L5640
and above
N/A
1333MHz
2 6
(12 DIMMs)
96GB RDIMM
X5650, L5640
and above
N/A
1066MHz
2
(12 DIMMs)
96GB RDIMM
E5620, L5630
and above
N/A
800MHz
2
(12 DIMMs)
96GB RDIMM N/A E5506, E5507
800MHz-
1333MHz
2
(8 DIMMs)
64GB RDIMM All All
Integrated Virtualization
All models of the x3620 M3 support a USB 2.0 Flash Key installed preloaded with VMware
ESXi 4.0 ESXi is an embedded version of VMware ESX 4.0, fully contained on the flash drive
and requiring no disk space—not an “ESX Lite.” Rather than management through a Service
Console based on a Linux operating system, ESXi relies on aggregate management tools,
including VirtualCenter, the Remote Command Line interface and the introduction of CIM for
standards-based and agentless hardware monitoring.
6 2 DIMMs per channel at 1333MHz is supported only with 1.5V RDIMMs.