IaaS vs PaaS vs SaaS
Infrastructure As A Service (IAAS) : It means of delivering computing infrastructure as on-demand services. IaaS customers can control their own data infrastructure without having to physically manage it on-site.
IaaS cloud infrastructure offers companies and administrators the best level of control and power over software and hardware, but they'll even be liable for ensuring their technologically secure and running properly to avoid causing outages.
Platform As A Service (PAAS) : It refers to cloud-based platform services that provide developers with a framework they can use to build custom applications upon.
PaaS isn't delivering software over the web, but it's providing a web platform that's accessible to different developers to make software delivered over the web.
PaaS products let developers build custom applications online without having to affect data serving, storage, and management.
The disadvantage of the PaaS model is you could have control what's built on the platform -- if there is an outage or issue with the hardware or operating system that the platform is made on, it'll remove the software with them.
Software As A Service (SAAS) : It refers to cloud-based software that is hosted online by a company and is available for purchase on a subscription basis and is delivered via the internet.
Here a cloud service provider is entirely responsible to manage software, and it's highly scalable, as it's deployed over cloud and users has to connect to it to avail the service.
Fault Domain / Update domain / Proximity Placement Group
Fault Domain : Virtual machines in the same fault domain share a common power source and physical network switch.
Update domain : Virtual machines in the same update domain will be restarted together during planned maintenance.Azure never restarts more than one update domain at a time.
Proximity Placement Group : A proximity placement group is a logical grouping used to make sure that Azure compute resources are physically located close to each other. Proximity placement groups are useful for workloads where low latency may be a requirement.
Azure Ultra Disks deliver high throughput, high IOPS, and consistent low latency disk storage for Azure IaaS VMs. Ultra Disk is suited for data-intensive workloads such as SAP HANA, top tier databases, and transaction-heavy workloads.
VM generation
Generation 2 VMs support features such as UEFI-based boot architecture, increased memory and OS disk size limits, Intel® Software Guard Extensions (SGX), and virtual persistent memory (vPMEM).
Generation 2 virtual machines support most 64-bit versions of Windows and more current versions of Linux and FreeBSD operating systems
Generation 1 virtual machines support most guest operating systems.
Enable OS guest diagnostics : Get metrics every minute for your virtual machine. You can use them to make alerts and stay informed on your applications.
Boot diagnostics
Use this feature to troubleshoot boot failures for custom or platform images. Boot diagnostics with managed storage account significantly improves creation time of Virtual machines by using pre-provisioned storage accounts managed by Microsoft.
Virtual Network Gateway : SKU
If the current SKU is Basic, Standard, or High performance, it can be upgraded or downgraded to a Basic, Standard, or High performance SKU.
If the current SKU is VpnGw1, VpnGw2, or VpnGw3, it can be upgraded or downgraded to VpnGw1, VpnGw2, or VpnGw3.
If the gateway is being created to coexist with an ExpressRoute gateway, choose any SKU except for Basic.
Locally-redundant storage : Locally redundant storage (LRS) replicates your data three times within a single physical location in the primary region.LRS protects your data against server rack and drive failures.
However, if a disaster like fire or flooding occurs then all replicas of a storage account using LRS could also be lost or unrecoverable.
Zone-redundant storage : Zone-redundant storage (ZRS) replicates your Azure Storage data synchronously across three Azure availability zones in the primary region. Each availability zone is a separate physical location with independent power, cooling, and networking.
ZRS by itself may not protect your data against a regional disaster where multiple zones are permanently affected.
Azure Storage offers two options for copying your data to a secondary region:
Geo-redundant storage (GRS) copies your data synchronously 3 times within one physical location within the primary region using LRS. It then copies your data asynchronously to one physical location within the secondary region.
Geo-zone-redundant storage (GZRS) copies your data synchronously across three Azure availability zones in the primary region using ZRS. It then copies your data asynchronously to one physical location within the secondary region.
The primary difference between GRS and GZRS is how data is replicated within the primary region.
Within the secondary region, data is usually replicated synchronously 3 times using LRS. LRS in the secondary region protects your data against hardware failures.
With GRS or GZRS, the info within the secondary region isn't available for read or write access unless there's a failover to the secondary region.
For read access to the secondary region, configure your storage account to use read-access geo-redundant storage (RA-GRS) or read-access geo-zone-redundant storage (RA-GZRS).
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