L4 - IAAS 1/2

Question 1

Who started the IAAS service model and what are the 3 components?

Answer 1

Amazon
- compute
- network
- storage

Question 2

Difference between regions and availability zones

Answer 2

AWS has regions and in these, there are availability zones that are no more than 100km apart. These availability zones are data centers.

Question 3

characteristics of availability zones

Answer 3

• two availability zones have no common points of failure –> servers in two zones are infrastructurally redundant

Question 4

Is communication free inside a zone?

Answer 4

Yes, but must be paid for between zones

Question 5

Two types of SLAs

Answer 5

• Region-level SLA which guarantees 99.99% regional availability (region is unavailable, when all of your running instances or running tasks, deployed in two or more AZs, concurrently have no external connectivity (so you have to replicate your services across two regions to claim the money))
• Instance-level SLA guarantees 99.99% reachability of an EC2 instance (instance is not available, when your Single EC2 instance has no external connectivity.)

Question 6

What does EC2 provide?

Answer 6

EC2 = Amazon Elastic Compute Cloud

• virtual machines running inside the Amazon Cloud
• Ephemeral storage (lasting for a very short time) tied to the VM (node) –> deleted when you delete the VM
• network-accessible block storage that persists across time and can be mounted in the VM
• virtual firewall to secure network in cloud

Question 7

What was E2C based on formerly?

Answer 7

XenHypervisor which was part of the software.
- Amazon Linux was domain 0 and Network I/O etc. always had to go through domain 0

Question 8

What is EC2 based on now?

Answer 8

• Nitro Hypervisor
• special interface cards now eliminate Domain 0.
• management happens in hardware instead of software DOM0
• Network I/O, CPU interrupts, Storage I/O now are in the hardware.
• limiters guarantee resource distribution

Question 9

What is an AMI/VM template?

Answer 9

Amazone Machine Image
- template that contains software configuration (e.g . OS)
- stored in S3

Question 10

4 AWS Storages

Answer 10

• Elastic Block Storage
• EC2 Instance Storage
• Elastic File System (EFS)
• Simple Storage Service (S3)

Question 11

Elastic Block Storage

Answer 11

(physical disks that are accessible through the network)

Question 12

EC2 Instance Storage

Answer 12

(physical disks that are connected to the server on which your VM will be placed)

Question 13

Elastic File System (EFS)

Answer 13

(network attached file storage)

Question 14

Simple Storage Service (S3)

Answer 14

(is an object storage service that stores data as objects within buckets. An object is a file and any metadata that describes the file. A bucket is a container for objects.)

Question 15

local storage solutions

Answer 15

SSD or HDD

Question 16

What is RAID?

Answer 16

Redundant Array of Independent Disks (RAID)
- type of storage that writes data across multiple drives within the same system
- inexpensive
- RAID 0: High performance without any redundancy
- RAID 1: Solid Data Protection with redundancy
- RAID 5: Balanced Data Protection and Speed (best of both worlds)

Question 17

What is non-volatile memory (NVM)?

Answer 17

type of computer memory that can retain stored information even after power is removed

Question 18

What is a SLC?

Answer 18

Single-level cell (SLC)
- SLC NAND stores only 1 bit of information per cell. The cell stores either 0 or 1 and as a result, the data can be written and retrieved faster.

Question 19

What are the pros and cons of SLC?

Answer 19

Pro: highest endurance and best performance
Cons: expensive and low capacities (not commonly used in consumer products)

Question 20

What is MLC?

Answer 20

Multi-level cell
MLV NAND stores multiple bits per cell (usually 2). Has a higher data density than SLC.

Question 21

What are the pros and cons of MLC?

Answer 21

Pros: cheaper than SLC
Cons: slower than SLC, lower write speeds, higher power consumption, more sensitive to data errors and hence a lower endurance

Question 22

Concerning data centers to what has the storage comparison moved?

Answer 22

It has moved from €/GB to €/IOPS

Question 23

Whatis IOPs?

Answer 23

Input/Output operations per second. It’s a measure of how many tasks (reading and writing data) a drive can carry out every second.

Question 24

What is an all-flash array for data center storage?

Answer 24

Only use flash storage or SSDs in combination with RAID. High IPOS, low latency, high bandwidth but it is expensive.

Question 25

3 ways of provisioning storage

Answer 25

• Direct Attached Storage
• Storage Area Network (SAN)
• Network Attached Storage (NAS)

Question 26

What is direct attached storage?

Answer 26

• storage devices that are attached to the individual computers
• leads to over-provisioning

Question 27

What SAN?

Answer 27

Storage Area Network (SAN)
Special, high-speed network that stores and provides access to large amounts of data
- network provides access to block-level data storage (disks)
- specialized network separated from LAN
- a shared pool of sparse resources
- client accesses the data as if it was a local hard drive/disk

Question 28

What are some SAN protocols used?

Answer 28

fibre channels, iSCSI (internet Small Computer System Inferface), ATA over Ethernet, HyperSCSI

Question 29

Cons of SAN?

Answer 29

• shared network bandwidth
• shared performance of storage devices
• security concerns due to transfer of data through network

Question 30

Pros of SAN?

Answer 30

• flexible distribution of devices between clients
• easy replacement of faulty servers
• easier disaster protection

Question 31

What is NAS?

Answer 31

Network Attached Storage (NAS)
- centralized storage device for storing data on a network
-connected to normal LAN network
- storage devices connected to a file server (access available at file-level for other computers)

Question 32

Cons of NAS

Answer 32

• a single point of failure

Question 33

SAN vs. NAS

Answer 33

SAN can be fibre channel based
NAS is connected to normal LAN network

SAN focuses on high performance and low latency
NAS focuses on ease of use, scalability, total cost of ownership (TCO)

NAS has access available at file level

Question 34

What is storage virtualization?

Answer 34

The process of pooling multiple storage devices’ physical storage space