Some of you might consider purchasing the Lenovo (formally IBM) System x servers. For the enterprise environments Lenovo offers x3850 X5 and x3850 X6 series. Since x3850 X5 will be discontinued from the market during this year, it makes sense to start considering x3850 X6. Such type of server will be mainly deployed for hosting the critical databases, virtualization and in the cloud environments. I’m sure that it will be mostly used as a hypervisor host in the environments, which host several hundreds or thousands of virtual machines.
X6 architecture has several significant improvements to X5, I’ll not describe the details, if you are interested I encourage you to read a Redbook. I want to focus on flexibility which 3850 X6 brings for everybody who does the capacity planning.
Benchmark
There is no mandatory performance comparison, which should do the vendors to follow. Let’s take those which are available on IBM website:
The x3850 X5 achieved 10,700 SAP SD benchmark users with 0.93 seconds average dialog response time 58,750 SAPS, measured throughput of 3,525,000 dialog steps per hour
The IBM System x3850 X6 achieved 25,000 SAP SD benchmark users with 0.98 seconds average dialog response time 136, 70 SAPS, measured throughput of 8,200,000 dialog steps per hour
According to SAG SD benchmark, x3850 X6 delivers double the performance of IBM System x3850 X5. IBM also provides with other benchmarks, you can find them here.
CPU
Let’s see what options we do have for CPU, as it is also an important aspect and goes hand in hand with memory capacity planning. 3850 X6 supports up to 15 cores of of E7 8xx/88xx v2 series, which is 50% more than 3850 X5.
x3850 X5 is available for up to four CPU 6, 8 and 10 cores E7 48xx/88xx series CPU.
x3850 X6 is available for up to four CPU 6, 8, 12 and 15 cores E7 48xx/88xx v2 series CPU.
Memory
x3850 X5 is quite sensitive in terms of properly assigned memory. x3850 X5 has 64 DIMMs, 16 per processor. If the memory is not installed according to the best practice there is a huge performance penalty, so the only way is to fill all memory banks. You should always end up with the following configuration:
2 GB modules – 128 GB
4 GB modules – 256 GB
8 GB modules – 512 GB
16 GB modules – 1 TB GB
32 GB modules – 2 TB
In the picture above you can see the limitation, the only option is to fill all memory banks not to loose performance.
On the other hand, architecture of x3850 X6 is different and brings more flexibility. x3850 X6 supports 4 – 64 GB memory modules, up to 96 DIMMs when all processors are installed – 24 DIMMs per processor.
Each processor has two integrated memory controllers, and each memory controller has two Scalable Memory Interconnect generation 2 (SMI2) links that are connected to two scalable memory buffers. Each memory buffer has two DDR3 channels, and each channel supports three DIMMs, for a total of 24 DIMMs per processors.
In general, x3850 X6 is very flexible in terms of memory sizing, you have various options how to combine the memory modules. Just don’t forget to follow the best practices described in the Redbook:
- When one DIMM per compute book is installed, system performance can be slow.
- For best performance, install DIMMs evenly across all four memory channels for each compute book.
- Higher capacity (ranked) DIMMs must be installed first. Follow the population sequence for the appropriate mode
Use case
When building or consolidating the virtual environment make sure you properly do capacity planning. Since 3850 X6 memory is scalable up to 6 TB, the limited factor in most of the cases will be the CPU. I would suggest to start with defining the scope, then continue with calculating the CPU requirements and at the end incorporate the CPU requirements to physical memory. 3850 X6 should give you sufficient flexibility to design the environment according your needs.
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It is really no brainier decisions to buy old x5’s nowadays, but also no huge reason to upgrade from them to x6 either