Administrator Guide

Appendix A Storage array cabling
21 Dell EMC Ready Solutions for HPC BeeGFS High Capacity Storage | ID 424
4.3 Scalable configurations
For the rest of the configurations, the performance numbers shown in Table 4 are estimates or extrapolations,
since scaling up is linear with addition of ME4084 arrays and scaling down by removing arrays is assumed to
be linear as well.
Performance and usable space of base and scalable configurations
Configuration
Small(S)
Medium(M)
Large(L)
L + S
L + M
2x L
Total U (MDS+SS)
18U
23U
33U
42U
47U
58U
# of ME4084
1
2
4
5
6
8
Estimated
usable
space
4TB
231 TiB
461 TiB
922 TiB
1153 TiB
1383 TiB
1844 TiB
8TB
461 TiB
922 TiB
1844 TiB
2305 TiB
2766 TiB
3688 TiB
12TB
691 TiB
1383 TiB
2766 TiB
3458 TiB
4149 TiB
5532 TiB
16TB
922 TiB
1844 TiB
3688 TiB
4610 TiB
5532 TiB
7376 TiB
Peak sequential read
≈ 6.8 GB/s
≈ 13.9 GB/s
≈ 23.7 GB/s
≈ 30.5 GB/s
≈ 37.6 GB/s
≈ 47.4 GB/s
Peak sequential
≈ 5.7 GB/s
≈ 11.5 GB/s
≈ 22.1 GB/s
≈ 27.8 GB/s
≈ 33.6 GB/s
≈ 44.2 GB/s
Sustained
performance
≈ 5 GB/s
≈ 11 GB/s
≈ 22 GB/s
≈ 27 GB/s
≈ 33 GB/s
≈ 44 GB/s
The sustained performance is the steady state performance of the solution stack over a longer period or for
more thread counts after the saturation has been attained. The more conservative approach would be to
consider the sustained performance to size a system rather than occasional peaks. But the peak performance
of the system as such shows the maximum extent to which the system could be pushed in terms of
performance or in other words the point where the performance hits the bottleneck and cannot grow any
further. All these numbers shown assume minimized caching effects since they are based off actual
measurements from the base configurations which were performed by minimizing caching effects.
BeeGFS usable space was calculated using the formula:
Estimate of BeeGFS Usable Space in TiB = 0.99 * Number of ME4084 arrays * 80
RAID HDDs per array * 0.8 * HDD size in TB * 10^12/2^40
Table 4 uses this formula to estimate the usable space of every configuration for each supported capacity of
the 7.2K RPM NL SAS HDDs.
The usable space is calculated in TiB. 0.99 is the factor considering the 1% overhead from the file system, a
conservation assumption. 80 is the number of HDDs per ME4084 excluding the hot spares. 0.8 is 80% of the
RAID 6 (8 + 2) HDDs being the data drives. The remaining 20% in the RAID volume are parity drives and are
not taken into consideration for usable space. The last factor in the fomula 10^12/2^40 is to convert the
usable space from TB to TiB.