Systems and Architecture Flashcards
1
Q
Define Round Robin
A
Distributes client requests across a group of servers. Going down the list of servers in the group, the round‑robin load balancer forwards a client request to each server in turn. When it reaches the end of the list, the load balancer loops back and goes down the list again
2
Q
Define Load Balancer
A
A load balancer sits between the client and the server farm accepting incoming network and application traffic and distributing the traffic across multiple backend servers using various methods
3
Q
Give an example of DNS load balancing
A
A company can have a single domain name and four absolutely identical company home pages on four physical servers based in Europe, Asia, North America, and Africa.
4
Q
Advantage of DNS Round Robin
A
It is simple to implement
5
Q
Troubleshoot one load balancer failure
A
If one load balancer fails, the secondary picks up the failure and becomes active. They have a heartbeat link between them that monitors status.
6
Q
Troubleshoot all load balancer failures
A
If all load balancers fail (or are accidentally misconfigured), servers down-stream are knocked offline until the problem is resolved, or you manually route around them.
7
Q
What is the Slash Dot Effect?
A
Also known as slashdotting, occurs when a popular website links to a smaller website, causing a massive increase in traffic. This overloads the smaller site, causing it to slow down or even temporarily become unavailable.
8
Q
Active-Active High Availability Cluster
A
An active-active cluster is typically made up of at least two nodes, both actively running the same kind of service simultaneously. The main purpose of an active-active cluster is to achieve load balancing. Load balancing distributes workloads across all nodes in order to prevent any single node from getting overloaded. Because there are more nodes available to serve, there will also be a marked improvement in throughput and response times.
9
Q
Active-Passive High Availability Cluster
A
An active-passive cluster consists of at least two nodes.. Not all nodes are active. The passive (a.k.a. failover) server serves as a backup that’s ready to take over as soon as the active (a.k.a. primary) server gets disconnected or is unable to serve.
10
Q
Define SATA
A
Serial Advanced Technology Attachment : is a serial communication method and began as an enhancement to the original ATA specifications, also known as IDE and, today, PATA
11
Q
SCSI
A
The Small Computer System Interface
12
Q
SAS
A
Serial Attached SCSI: is a type of SCSI that uses serial operation rather than parallel as the original SCSI did.
13
Q
IDE
A
Integrated development environment
14
Q
PATA
A
Parallel Advanced Technology Attachment
15
Q
Define NAS
A
Network Attached Storage:
- Name given to a dedicated storage unit that can be directly attached to the network.
- Transfers data as files.
- Transfers files over local area network. (i.e. ethernet, wireless, fiber)
16
Q
Define SAN
A
Storage Area Network
- It is a network that consists of storage units.
- Transfers data as blocks.
- Transfers blocks over wide area network using FCIP or iSCSI media.
17
Q
FCIP
A
Fibre Channel over IP
18
Q
iSCSI
A
Internet Small Computer Systems Interface
- an IP-based networking storage standard method of encapsulating SCSI commands within IP packets.
- Allows you to use the same network for storage that you use for the balance of the network.
- Can be used in a NAS
- First used in a SAN.
19
Q
RAID
A
Redundant array of independent risks
-RAID arrays often use caching to improve performance
20
Q
RAID 0
A
- Disk Striping with no parity.
- Need at least 2 Disks
- No Fault Tolerance
21
Q
RAID 1
A
- Disk Mirroring
- Needs at least 2 Disks.
22
Q
RAID 5
A
- Disk Striping with parity
- Need at least 3 Disks
- Most Widely used
23
Q
RAID 0+1
A
- Disk Striping + Disk Mirroring.
- For every disk striping, there needs to be one mirroring it.
- 2 Disk Striping = 2 Disk Mirroring. 1:1 Ratio
24
Q
What is Backplane?
A
- Provide data
- Control signal connectors for the hard drives.
- Provide the interconnect for the front I/O board, power and locator buttons, and system/component status LEDs.
When a backplane fails, it affects all the drives that connect to it.
-Backplane failures are less likely than drive failures
25
Types of RAID failures
RAID arrays often use caching to improve performance.
- A battery-backed cache is one that can maintain the data in the cache during a power outage, preventing the loss of data still residing in the cache at the moment of the power failure. When this battery fails, it can cause the loss of data.
- Disk failure disk is unable to be accessed, data corrupted, unusual noises from the disk (click of death).
26
Cache
Hardware or software that is used to store something, usually data, temporarily in a computing environment.
When the cache is turned off, you lose all of those performance benefits. Cache can be enabled in both the operating system and in the storage software.
27
Ways to prevent RAID failure
- No SPOF
- Secondary/backup RAID controller/disks
- Monitoring systems to identify issues before they become a failure
- Cloud based backup
28
Full Backup
- All Data is backed-up
- Slowest backup time
- Fastest restore time
- High storage space
29
Incremental Backup
- New/Modified data backed-up
- Fast backup time
- Slower restore time
- Low storage space
30
Differential Backup
- All data since last full backed-up
- Moderate backup time
- Faster restore time
- Moderate storage space
31
NFS
Network File System
32
SMB
Server Message Block
33
AFS
Andrew File System
34
Types of Storage failures
- Loss of data/data corruption
- Security issues
- Loss of connectivity
- Exposure of data
35
HBA
Host Bus Adaptor
36
What is a Fibre channel switch?
A network switch compatible with the FC protocol. It allows the creation of a Fibre Channel fabric, that is the core component of a SAN
37
Troubleshoot HBA failures
- Check cables
- Reseat the adaptor in its slot
- Implement redundant HBAs
- If the HBA fails it is a SPOF
38
FCoE
Fibre Channel over Ethernet
| -Encapsulates Fibre Channel traffic within Ethernet frames -Unlike iSCSI, it does not use IP at all.
39
Causes and consequences of SAN failures over FCoE
-TCP/IP misconfiguration (inability for some / all nodes to access storage;)
-Failure of a single NIC (increased load on remaining
NIC on a single node and possible reduced throughput for this node or complete
outage if this is the only onboard NIC)
-incorrect / invalid LUN (inability to access logical storage
device)
-loss of network - total outage.
- single misconfiguration or failed standard switch (increased load on remaining
switches and possible reduced throughput or storage outage. The standard data
network may also be impacted;)
40
Causes and consequences of storage area network (SAN) failures over the FC protocol
-single misconfigured or failed Fibre switch
-Loss of all Fibre switches (complete loss of access to storage. The standard data
network is unaffected)
-Failure of a single HBA (increased load on remaining HBA on a
single node and possible reduced throughput for this node or complete outage if this
is the only onboard HBA.)
41
misconfigured NFS
loss of access for Linux/ NAS network shares
42
misconfigured SMB
loss of access to Windows network shares
43
misconfigured AFS
loss of access for Apple systems shares
44
misconfigured authentication /authorisation
-loss of access to some / all NAS
45
What is a LUN
Logical Unit Number
-A number used to identify a logical unit, which is a device addressed by the SCSI protocol or SAN protocols which encapsulate SCSI, such as Fibre Channel or iSCSI.
46
LUN masking
The process of controlling access to a LUN by effectively “hiding” its existence from those who should not have access. This makes the storage available to some hosts but not to others.
47
Causes and consequences of SAN failures over the iSCSI
-single misconfiguration or failed standard switch (increased load on remaining
switches and possible reduced throughput or storage outage. Standard data network)
may also be impacted;
-TCP/IP misconfiguration (Inability for some / all nodes to access storage;)
-failure of a single NIC (increased load on remaining NIC on a single node and
possible;)
-reduced throughput for this node or complete outage if this is the only onboard NIC.
-incorrect / invalid IQN address (inability to access logical storage device)
48
IQN
iSCSI Qualified Name
- Logical name that is not linked to an IP address
- Unique
49
Causes and consequences of cloud storage failures
-router / ISP failure (complete loss of access;)
-TCP/IP misconfiguration (inability for some / all nodes to access storage;) -misconfigured authentication / authorisation (loss of access to some / all cloud
storage;)
-cloud service provider failure (loss of access to data and / or loss of data.)
50
Types of cloud services
OneDrive, Dropbox, Google Drive, Amazon EC2 and Microsoft Azure.
51
Causes and impact of computer system failures (Hardware)
- memory component failure (individual node crash;)
- SSD/HDD failure (system crash and possible loss of data;)
- CPU failure
- power supply
- cooling (intermittent crash or possibly permanent damage to components)
- Heated/power related issues
52
SSD/HDD
Solid State Drive/Hard disk drive
53
Causes and impact of network failures
- NIC failure (loss of access from/to one network node;)
- Switch failure (loss of access to LAN;)
- Router failure (loss of access to WAN;)
- Firewall (blocked IP's, no protocols, ports;)
- Web proxy (No internet access)
- Cabling - incorrect cable type (straight through / cross over or exceeding recommended lengths and / or EMI)
- Wireless (exceeding maximum distance and / or EMI or RFI|)
54
EMI/RFI
Electromagnetic interference/ Radio-frequency interference
55
Patches and Hotfix
- Patch - Publicly released update to fix a known bug/issue.
- Hotfix - update to fix a very specific issue, not always publicly released
56
Causes and impact of incorrectly applied / faulty patches
- intermittent problems / complete loss of function;
- failure to boot OS.
- cause a system to crash
57
Causes and impact of IP Addressing configuration errors
- loss of access to some / all LAN / WAN / nodes
- Invalid IP address (address conflicts with other computers and network configuration problems.)
- DHCP error causing DNS errors
- Incorrect subnet mask-(communications fail to some nearby networks)
- Incorrect Default Gateway (can communicate with hosts on its own network segment, but will fail to communicate with hosts on some or all remote networks.)
58
Causes and impact of VLAN configuration errors
- VLAN in a down state
- interface flapping on a port set for access-only mode
- VLAN trunking issues (trunk is still not establishing across the configured link)
- VLAN routing issues (VLANs cannot reach one another)
59
Causes and impact of excessive heat
- Shorten the lifespan of a system leading to premature failure.
- Excessive heat can cause a system to crash
- Excessive dust can also lead to heat build-up
60
HVAC
Heating Ventilation and Air Conditioning are vital components of the server room they should be monitored and secure, tampering with HVAC can cause a DoS attack
61
Causes and impact of a lack of power
- intermittent problems;
- system reboots;
- complete loss of systems;
- data loss
- Blackout/brownout
62
Causes and impact of EMI / RFI
- Data loss
| - The amount of interference and frequency will dictate how much interference is caused
63
EMI/RF
Electromagnetic interference/Radio frequency
64
Causes and impact of backup failure
- Data loss
- Data corrupted
- Virus
- Physical damage
- misconfigured backup / restore
65
Malware
Malicious software- Programs designed to infiltrate and damage computers without the users consent
66
Causes and impact of malware infection
- Lack of user training- results to loss of data
- insufficient anti-malware tools
- poorly configured firewall
67
Worm
Malware which is self-replicating
68
Trojan
- Malware which is disguised as something useful or legitimate
- Illegal downloads, games, screensavers or system software
- Used to install DDoS Zombies/Bots
69
Rootkit
- Malware which embeds itself in the heart of the OS
| - Once infected the system normally has to be completely reinstalled
70
Botnets
- malware which infects numerous systems that are controlled by a hacker
- Used in DoS/DDoS attacks
- IRC used to connect with a botnet
71
IRC
Internet Relay Chat
72
Ransomware
- Malware which demands payment
| - WannaCry most well known Ransomware
73
DOS
Denial Of service
-A type of attack which has the primary objective of preventing target systems from performing properly or responding at all
74
DDOS
Distributed DoS
- infiltrate intermediate systems to provide launch platforms.
- May use Trojans, Bots, Zombies or Botnets
75
Common DOS attacks
- Smurf
- Fraggle
- Land attack
- Ping of Death
- SYN Flood
76
Smurf
using ping packets against the broadcast address so the replies return to the victim causing an overload
77
Fraggle
similar principal to the Smurf but using UDP packets against the broadcast address so the ICMP reply returns to the victim
78
Land attack
the packets received by the victim contain identical source and destination addresses, generating confusion of the target
79
Ping of Death
sending a ping packet that is too large, causing a crash
80
SYN Flood
exploits the TCP three-way handshake process
81
Spam
Unsolicited/Unwanted Email which may be used for the following:
Transportation of Malware
Social Engineering
DoS
82
Causes and impact of poor wireless security
- weak encryption / poor selection of passphrase
- Rogue Access Points/Ad-Hoc Networks
- DOS
- Configuration Problems (Mis-Configurations/Incomplete Configurations)
83
Causes and impact of a failure to implement physical security.
- unauthorised access
- Loss of data
- Theft
- Natural disaster
84
Causes of network latency
- Storage Delays
- Routers
- jitter on time critical services such as poor quality VOIP / video conferencing
85
Causes of lack of bandwidth
- Malware
- poor cabling
- junk software
- slow videos
- slow file transfers
86
Causes of lack of storage capacity
- lack of maintenance
- neglecting to plan for future storage needs
- system failure producing large files
- Systems slowdown/crash/freeze
87
Causes of lack of memory
- system runs slow
- disk thrashing
- system lockup/crash
- application memory leaks
88
Memory Leaks
- Bugs- fails to release memory when no longer needed
- affects particular application and OS
- reduces system performance
- full system freeze
89
CPU Performance
```
-Core
processors have one or more
operates as an individual CPU
Internal speed
MHz/GHz
-Bus
speed which motherboard communicates with CPU
-Cache
high speed
expensive memory
located on the CPU
L1,L2,L3 cache
```
90
Common network devices
-Router
-Firewall
-Switch
-Hub
-NIC
-IPS
IDS
91
Layer 2 Switch
A type of network switch or device that works on the data link layer (OSI Layer 2) and utilizes MAC Address to determine the path through where the frames are to be forwarded. It uses hardware based switching techniques to connect and transmit data in a local area network (LAN).
92
Layer 3 Switch
Combines the functionality of a switch and a router.
- acts as a switch to connect devices that are on the same subnet or VLAN
- lightning speeds
- IP routing intelligence built into it to double up as a router.
93
Cisco's Three layered model
| Core layer
-Backbone of network
-provides fault isolation and backbone connectivity.
switches traffic at the highest speeds
-level of redundancy, used in case of link or hardware failure
94
Cisco's Three layered model
| Distribution layer
- communication point between the access and the core layer.
- handles the routing, packet filtering, WAN access and determines how packets can reach the core if needed.
- includes all OSI Layer 3 devices, such as routers and layer 3 switches.
95
Cisco's Three layered model
| Access layer
- desktop layer
- Connects client devices on the internal network
- separates collision domains, filter MAC addresses and implement load balancing.
- uses Ethernet
96
VLAN
- Switches provide a method of broadcast domain segmentation called Virtual LANs (VLANs)
- Layer 2 method of creating more broadcast domains
- VLANs logically divide a switch into multiple, independent switches at Layer 2, each in their own broadcast domain
97
Static Routing
-manually-configured routing entry
98
Dynamic routing
- enables routers to select paths according to real-time logical network layout changes
- RIP
- OSPF
99
RIP
Routing Information Protocol
100
OSPF
Open Shortest Path First
101
WAP
Wireless access point
- Hardware device on a LAN
- allows wireless and wired networks to connect through a wireless standard
102
Wireless routers.
- enables wireless network packet forwarding and routing
- serves as an access point in a LAN
- Like a wired router but replaces wires with wireless radio signals to communicate within and to external network environments
103
Stateful Firewall
- Firewall compares current packets to previous ones.
- slower than packet filters, but are far more secure.
- tracks the operating state and characteristics of network connections travelling through it
- Only packets matching a known active connection are allowed to pass the firewall.
104
Stateless Firewall
- watch network traffic and restrict or block packets based on source and destination addresses or other static values.
- not aware of traffic patterns and data flow
- uses simple rule-sets
105
Firewall Deep packet Inspection
-data processing that inspects in detail the data being sent over a computer network, and usually takes action by blocking, re-routing, or logging it accordingly
106
IPS
intrusion prevention systems
| -traffic has to go through the device which has the ability to be proactive and block the suspect traffic
107
IDS
intrusion detection systems
- are placed on segments of a network so they can detect unauthorised activity or malicious traffic
- Does not prevent traffic from reaching the network
108
NIDS
Network intrusion detection system
| -monitors segments for malicious traffic or it can be host based
109
HIDS
Host-based intrusion detection system
| -installed on a host and monitors traffic coming into the host, and also local activity on the host
110
Honeypot
- Used to monitor intrusion / attacks and conduct intelligence gathering
- Used to deflect potential attacks
111
Tower server
- reside on shelves
| - looks like your usual server for desktop
112
Rack mounted server
- Bolted into a framrack called a rack
- Gets equipment of the floor
- good for space
113
Blade Server
- houses multiple circuit boards/server blades
| - uses less space
114
Types of OS servers
- Red hat enterprise Linux
- Windows server
- Mac OS X server
115
Server OS Key features
- have access to the server both in GUI and command level interface
- execute processes from OS commands
- advanced level hardware, software and network config services
- central interface to manage users/ security
- Shares resources to client systems
- Stores resources centrally for easy management
116
Client OS Features
- works within computer desktops and various portable devices.
- only supports a single user.
- Smartphones and small computer devices are able to support client operating systems
117
Active directory
| server
- several services that run on windows server
- manages permissions and access
- users/groups/device
118
DNS
| server
- Domain Name System
- database of public IP addresses/hostnames
- Translates names into IP adresses
119
Web Proxy
| server
- hides IP adress from websites
| - act as shields between you and the website
120
File and Print
| server
- generic term for any computer that is being used to provide file storage and printing for other computers.
121
Email
| Server
- handles and delivers e-mail over a network
| - receive e-mails from client computers and deliver them to other mail servers
122
Database
| server
- data analysis
- storage
- data manipulation,
- archiving
- other non-user specific tasks.
123
Virtualisation
| server
- partitions a physical server into a number of small, virtual servers
- each virtual server runs multiple OS instances at the same time
124
Type 1 hypervisors
- runs on bare metal
- runs directly on the host machine's physical hardware
- most efficient
125
Type 2 hypervisors
- runs on top of an OS
- relies on the host machine's pre-existing OS to manage calls to CPU, memory, storage and network resources.
- eg. VMware Fusion
126
VMM
Virtual machine monitor
| -intermediates between the host and the guest VM
127
Public Cloud
-provides the infrastructure and services over the public internet and are hosted at the cloud vendor’s premises.
128
Private Cloud
cloud infrastructure that is meant for use exclusively by a single organization.
129
Hybrid Cloud
-uses a combination of at least one Private and one Public Cloud.
130
PaaS
Platform As A Service
- Cloud based computing system and associated software (OS + Application package)
- provides a platform for software creation
131
SaaS
Software As A Service
- Cloud based software/application packages
- utilizes the internet to deliver applications
- majority of SaaS applications run directly through your web browse
132
IaaS
Infrastructure As A Service
- Cloud based systems being completely
- self-service for accessing and monitoring computers, networking, storage, and other services outsourced
133
Example of SaaS
- Google Apps,
- Dropbox
- Cisco WebEx
134
Example of PaaS
- Windows Azure
| - AWS Elastic Beanstalk
135
Example of IaaS
- AWS
| - Microsoft Azure
136
Function of VDI
Virtual desktop infrastructure
- technology for providing and managing virtual desktops
- hosts desktop environments on a centralised server and deploys them to end clients on request.
137
Middleware
- software glue
- acts as a bridge between OS and applications on a network
- enables communication and data management for distributed applications.
- provides a framework for the forwarding and queuing of transactions
138
SOAP
Simple object access protocol
| -interchange data between applications which are built on different programming languages.
