Dell PowerConnect W
AirWave 7.1
Sizing Guide
Contents
Overview ................................................................................................................................................................................... 4
High Level Sizing Information ................................................................................................................................................... 4
Storage Matrix.................................................................................................................................................................... 5
CPU & BIOS ................................................................................................................................................................................ 5
Intel Nehalem and Westmere Architecture Information .......................................................................................... 5
AMD Information ............................................................................................................................................................... 5
Operating System ..................................................................................................................................................................... 6
Storage ...................................................................................................................................................................................... 6
RAID Configuration Information ..................................................................................................................................... 6
Disk Partitioning ................................................................................................................................................................. 7
Storage System Tuning .................................................................................................................................................... 7
Virtualization ............................................................................................................................................................................. 8
Virtualized Processing and Disk IOPS Matrix.............................................................................................................. 8
Scalability Assumptions ........................................................................................................................................................... 9
Wireless ............................................................................................................................................................................... 9
Wired .................................................................................................................................................................................... 9
VisualRF ............................................................................................................................................................................... 9
Appendix ................................................................................................................................................................................. 11
AWMS Appliance ............................................................................................................................................................ 11
AWMS Server Reference Sell ...................................................................................................................................... 11
Super AMP (2,500 + Devices) BOM ............................................................................................................................. 11
AMD Hardware Matrix ................................................................................................................................................... 12
Overview
Managed
Devices
CPU Class
Clock
Speed
(GHz)
CPUs
Total
Cores
AWMS
Memory
RAPIDS
Memory
VisualRF
Memory
Pilot
1-25 APs
Quad Core Intel®
Xeon X3430
2.4 1 4
3 GB
.5 GB
.5 GB
100
Quad Core Intel®
Xeon X3440
2.53 1 4
4 GB
1 GB
1 GB
200
Quad Core Intel®
Xeon X3460
2.8 1 4
4 GB
2 GB
2 GB
500
Quad Core Intel®
Xeon X5540
2.53 1 4
4 GB
2 GB
2 GB
1,000
Quad Core Intel®
Xeon X5560
2.8 1 4
6 GB
3 GB
3 GB
2,500
Quad Core Intel®
Xeon X5560
2.8 2 8
16 GB
4 GB
4 GB
2,500 +
Hex Core Intel®
Xeon X5680
3.33 2 16
24 GB
6 GB
6 GB
This document provides guidelines for purchasing new hardware which will host the Dell
PowerConnect W AirWave Wireless Management System (AWMS). Your hardware should
incorporate margin for WLAN expansion as well as future AWMS features and modules. These
specifications are formulated to keep AWMS running on the same hardware platform for up to two
years.
Factors which influence the processing requirements for your AWMS server:
How many devices will the server manage?
How often will AMP communicate these devices?
How many wireless clients will the server monitor?
Will this server run the RAPIDS (IDS and WIPS) modules?
Will this server run VisualRF and provide location services?
High Level Sizing Information
CPU and Memory Matrix
Storage Matrix
# of
Devices
Min. AWMS
Storage
Max. AWMS
Storage
*IOPS
2 x random writes to
reads
Storage System
100
*75 GB
75 GB
60
(1) Drive 15K RPM
200
75 GB
75 GB
120
(1) Drive 15K RPM
500
75 GB
75 GB
300
Multiple 15K RPM RAID Drives
1,000
75 GB
150 GB
600
Multiple 15K RPM RAID Drives
2,500
187 GB
375 GB
1,500
Multiple 15K RPM RAID Drives
2,500 +
300 GB
600 GB
3,000
Multiple 15K RPM & SSD RAID Drives
Note: Please ensure the disk subsystem can sustain these random write rates. Sustained sequential write rates will
not help, because AWMS writes are primarily random.
* The 75 GB requirement on the smaller installation (100-500) accounts for the OS and swap overhead,
plus it is very difficult to install a single disk with less 75 GB capacity.
CPU & BIOS
Intel Nehalem and Westmere Architecture Information
With the advent of Nehalem, Intel makes a giant leap in the FSB to support NUMA (Non Uniform
Memory Access). In NUMA, memory on the same processor board as the CPU (local memory) is
accessed faster than memory on other processor boards (shared memory), hence the "non-uniform"
nomenclature. As a result, NUMA architecture scales much better to higher numbers of CPUs/cores
than SMP.
32-bit - ensure NUMA is disabled.
Some vendors’ BIOS refer to non NUMA as “Memory Node Interleaving”. Ensure
“Memory Node Interleaving” is “Enabled” on 32-bit operating systems.
By default most vendors disable this setting in their BIOS.
64-bit - ensure NUMA is enabled. Some vendors’ BIOS have “NUMA Enabled” or “NUMA-Aware
OS” options.
Ensure Power Management is configured to “Maximum Performance.” By default most vendors
configure BIOS to an eco-friendly setting.
Ensure Memory Operating Mode is configured to “Optimizer Mode” if available.
AMD Information
Dell does not actively conduct scalability testing for the AMD processor product line. These numbers
are based on published performance data versus the Intel product line. See Appendix below for details
in the AMD Scalability Matrix.
Operating System
To ensure hardware capability purchase server hardware that is certified to by Red Hat Enterprise
Linux.
AWMS includes the CentOS operating system based on Red Hat Enterprise Linux and is installed
by default. You may choose to use Red Hat Enterprise Linux.
AWMS supports both 32-bit and 64-bit hardware platforms. An AWMS server servicing more
than 2,500 devices requires 64-bit OS installation coupled with AWMS 7.1 or higher.
AWMS 7.1 installs 64-bit CentOS by default.
Storage
AWMS stores most statistical data in special statistical flat files. This serves two purposes. First, it
improves speed, because writing to a statistical flat file is much faster than writing to a relational
database. Secondly, it provides for a known, fixed amount of storage per managed device. Last, it
consumes much less space than a traditional rational database. AMP spends much more time writing to
the disk subsystem than reading from it.
Here are some factors which influence storage requirements for your AWMS server.
How many devices will the server manage?
How much historical data will the server retain?
How many wireless clients will the server monitor?
Will this Server run VisualRF and RAPIDS?
RAID Configuration Information
AWMS 100 and 200 models perform well on a single, fast (spindle speed) disk.
RAID configuration requires at least 4 SAS/SCSI disk drives in a RAID-10 configuration supplied via a
hardware controller with at least 256 MB of cache. All disk drives must have 15K RPM spindle speeds.
Do not use software raid systems or SATA disk drives.
RAID configuration requires at least 6 SAS/SCSI disk drives in a RAID-10 configuration supplied via a
hardware controller with at least 512 MB of cache. All disk drives must have 15K RPM spindle speeds.
These large servers mandate two distinct disk partitions. The first partition will require 10 SSDs (Solid
State Disk) drives in RAID-10 configuration supplied via a hardware controller with at least 512 MB of
cache. This partition is the high throughput data storage area “/var” described in the partition table
below.
The second partition will required 2 SAS/SCSI drives in a RAID-1 configuration supplied via a hardware
Note: Please contact http://support.dell.com when purchasing or configuring any hardware platform servicing more
than 2,500 devices. AWMS servers servicing more than 2,500 devices require 64-bit OS and AWMS 7.1 or higher. Do
not use software raid systems or SATA disk drives.
Default Partitions
Size
boot
100 MB
swap
Twice size of RAM
/
Rest of disk space
Default Partitions
Purpose
Recommended Size
boot
Boot partition
100 MB
swap
Swap partition
Twice size of RAM
/
AWMS
25% of total disk space
/alternative
Database backup location
10% of total disk space
/var/log
All log from all services
5% of total disk space
/var/lib/pgsql
PostgreSQL database files
25% of total disk space
/var/airwave/rrd
Statistical flat files
25% of total disk space
/var/airwave-backup
Nightly backup location
10% of total disk space
Note: Please ensure the disk subsystem can sustain these random write rates. Sustained sequential write rates will
not help, because AWMS writes are primarily random.
There could be upgrade or installation issues when manually partitioning your disk subsystem.
controller. Both drives must have 15K RPM spindle speeds. This partition will contain the operating
system.
Disk Partitioning
AWMS automatically partitions the disk subsystem upon installation. You can override these values.
The table below lists the default partitioning and provides guidance for more advanced scenarios.
Storage System Tuning
Ensure all disks are configured to “One Virtual Disk”.
If the RAID controller has battery-backed cache, ensure the Write Policy is configured to “Write-
Back”, otherwise ensure it is configured to “Write-Through”.
CentOS and RH Linux include four custom schedulers to handle I/O.
Note: Contact http://support.dell.com prior to changing this setting.
Managed
Devices
CPU Class
Clock
Speed
(GHz)
CPUs
Total
Cores
Max
Memory
Sustained
IOPS
Pilot
1-25 APs
Quad Core Intel® Xeon X3430
2.4 1 4
3 GB
30
100
Quad Core Intel® Xeon X3440
2.53 1 4
6 GB
60
200
Quad Core Intel® Xeon X3460
2.8 1 4
8 GB
120
500
Quad Core Intel® Xeon X5540
2.53 1 4
8 GB
300
1,000
Quad Core Intel® Xeon X5560
2.8 1 4
12 GB
600
2,500
Quad Core Intel® Xeon X5560
2.8 2 8
24 GB
1,500
2,500 +
Hex Core Intel® Xeon X5680
3.33 2 12
48 GB
3,000
Note: There are always spikes that go beyond the Sustained IOPS numbers stated above. Dell recommends a 20 %
increase buffer for virtualized environments. Ensure you allocate enough extra disk space for the OS and swap when
partitioning the virtual disk.
CFQ - Completely Fair Queuing is the default algorithm
Deadline elevator - uses a deadline algorithm to minimize I/O latency
NOOP scheduler – is a simple FIFO
Anticipatory elevator – introduces a small delay before dispatching the I/O
While CFQ works well in most installations, Dell has found changing scheduler to NOOP and allowing
the hardware RAID controller to handle I/O queuing has produce significant I/O improvements. This is
set via /sys/block/<device>/queue/scheduler.
Virtualization
AWMS will run in a VmWare and Xen virtualized environment. To ensure scalability you need to
dedicate the processing and memory described in the table below. You must also ensure that the disk
subsystem can maintain the IOPS throughput detailed below.
Most virtualized environments utilize a shard disk subsystem assuming that each application will have
bursts of I/O without a sustained high I/O throughput. AWMS requires a continuous sustained high
data I/O rate.
Virtualized Processing and Disk IOPS Matrix
Scalability Assumptions
Category
Value
Average density of client devices per access point
5
Device configuration auditing interval
Daily
Up/Down status polling period (minutes)
5
User data polling period (minutes)
10
Thin AP discovery period (minutes)
15
Device-to-device link polling period (minutes)
20
Device bandwidth polling period (minutes)
10
802.11 counters polling period (minutes)
15
Rogue AP and device location data polling period (minutes)
30
CDP neighbor data polling period (minutes)
60
Note: Auditing more than once a day can have a tremendous impact on scalability.
Category
Value
Ratio of switches/routers to access points
20%
Average port density of switches/routers
36
Read ARP polling period (hours)
8
Read CDP table for device discovery polling period (hours)
8
Read bridge forwarding table polling period (hours)
8
Interface polling period (minutes)
10
Category
Value
Average floor plan size (feet)
62,500
Number of access points per floor plan
20
Dell continually test scalability based on the following assumptions. Deviations from these
assumptions can impact overall scalability of your AWMS server.
Wireless
Wired
VisualRF
Number of clients per floor plan
100
Number of attenuation grid cells per floor plan
2,500
Number Rogue devices per floor plan
20
AMP Synchronization timer (minutes)
15
Rogue location timer (minutes)
30
Location calculation timer (min/max/number of samples)
90/360/3
Appendix
SKU
CPU Class
Clock
Speed
(GHz)
CPUs
Total
Cores
Memory
Disk Subsystem
AWMS-HW-PRO
Quad Core Intel®
Xeon® X5560
2.8 1 4
12 GB
(4) 73GB, 15K RPM - Raid 10
146 GB of usable disk space
AWMS-HW-ENT
Quad Core Intel®
Xeon® X5560
2.8 2 8
24 GB
(6) 146GB, 15K RPM - Raid 10
438 GB of usable disk space
Managed
Devices
Clock
Speed
(GHz)
CPUs
Total
Cores
Memory
Disk Subsystem
2,500
2.93 2 8
24 GB
(6) 146GB, 15K RPM - Raid 10
438 GB of usable disk space
Category
Part Numbers
Description
Qty
Motherboard
18 Dimm Xeon 5520 (Tylersburg) ServerBoard - UIO, 192G
1
CPU
X5680
Westmere 6C 3.3Ghz
2
Memory
2 GB - DIMM 240-pin - DDR3
18
OS Disk
ST9146852SS
SEAGATE 2.5" 146GB SAS 2.0 15K RPM
2 Data Disk
AWMS Appliance
Dell provides the option of purchasing a specially designed hardware appliance. There are two models
listed below. AWMS-HW-PRO is designed for deployments with up to 1,000 devices. AWMS-HWENT is designed for deployments up to 2,500 devices.
AWMS Server Reference Sell
Dell has partnered with the leading server manufacturers to certify specific hardware platforms for
capability and scalability.
Super AMP (2,500 + Devices) BOM
This is a sample bill of material for Super AMP which can support more than 2,500 devices. Please
contact
SSDSA2SH064G1
Intel 2.5” 64 GB SSD, X25-E SLC, 7.0 mm
14
RAID Controller
AOC-USASLP-H8iR
SAS 3Gb/s Eight-Internal ports RAID Adapter
1
Managed
Devices
CPU Class
Clock
Speed
(GHz)
CPUs
Total
Cores
AWMS
Memory
RAPIDs
Memory
VisualRF
Memory
500
Quad Core AMD Opteron™ 8387
2.8 1 4
4 GB
2 GB
2 GB
1,000
Quad Core AMD Opteron™ 8387
2.8 2 8
10 GB
3 GB
3 GB
2,000
Quad Core AMD Opteron™ 8435
2.6 2 12
12 GB
6 GB
6 GB
Note: Dell does not actively conduct scalability testing for the AMD processor product line. These numbers are based
on published performance data versus
AMD Hardware Matrix
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