on 14-Nov-2019 (Thu)

Question

One category of statistical dimension reduction techniques is commonly called principal components analysis (PCA) or the singular value decomposition (SVD). These techniques generally are applied in situations where the rows of a matrix represent *** of some sort and the columns of the matrix represent *** or *** (but this is by no means a ***).

Answer

One category of statistical dimension reduction techniques is commonly called principal components analysis (PCA) or the singular value decomposition (SVD). These techniques generally are applied in situations where the rows of a matrix represent observations of some sort and the columns of the matrix represent features or variables (but this is by no means a requirement).

Question

Recommendation for producion environment:

Failovercluster SQL

Answer

Recommendations

In a production environment, we recommend that you use static IP addresses in conjunction the virtual IP address of a Failover Cluster Instance. We recommend against using DHCP in a production environment. In the event of down time, if the DHCP IP lease expires, extra time is required to re-register the new DHCP IP address associated with the DNS name.

Question

In AWS, in Route 53, when you register a new domain (like kkhosravi.com), a [...] [...] with the same name as your domain is automatically created that acts as the DNS service that will route traffic (via A records, CNAME records, etc) for your domain (kkhosravi.com) and subdomains (e.g. test.kkhosravi.com)

Answer

Hosted Zone

Question

In AWS, for Route 53, when you register a new domain (like kkhosravi.com), and the corresponding Hosted Zone with the same name is created (that contains all the A records, CNAME records, etc for routing traffic for your domain and subdomains), two records are created automatically: the [...] records and the SOA record.

Answer

NS

^^ the NS record identifies the name servers for the hosted zone (e.g. samsungknox.com NS ns-650.awsdns-17.net 172800TTL). Note if you switch DNS service away from Route53 to another service, the TTL becomes a factor and it could take 172800 seconds (48 hours) for the changes to propegate across the internet.
^^^ the SOA (Start of Authority) record provides information about a domain and the corresponding Amazon Route 53 hosted zone. (e.g. samsungknox.com SOA ns-650.awsdns-17.net awsdns0hostmaster.amazon.com 1 7200 900 1209600 86400
^^^^ You do not need to ever edit these as they are created automatically when you register your domain with Route53 (or are imported if you say use godaddy.com for the domain name registration)

Question

In AWS, for Route 53, when you register a new domain (like kevinkhosravi.com), and the corresponding Hosted Zone with the same name is created (that contains all the A records, CNAME records, etc for routing traffic for your domain and subdomains), two records are created automatically: the NS records and the [...] record.

Answer

SOA (Start of Authority)

^^ the NS record identifies the name servers for the hosted zone (e.g. samsungknox.com NS ns-650.awsdns-17.net 172800TTL). Note if you switch DNS service away from Route53 to another service, the TTL becomes a factor and it could take 172800 seconds (48 hours) for the changes to propegate across the internet.
^^^ the SOA (Start of Authority) record provides information about a domain and the corresponding Amazon Route 53 hosted zone. (e.g. samsungknox.com SOA ns-650.awsdns-17.net awsdns0hostmaster.amazon.com 1 7200 900 1209600 86400
^^^^ You do not need to ever edit these as they are created automatically when you register your domain with Route53 (or are imported if you say use godaddy.com for the domain name registration)

Question

In AWS, for Route 53, an [...] record is a type of record (usually a type of A record) that maps your domain/subdomain name (e.g. test.kkhosravi.com) to the DNS of an AWS resource (e.g. ELB, CloudFront Distribution, etc), instead of mapping the A record directly to an IP.

Answer

Alias

Question

In AWS, for Route 53, you cannot use a [...] record for your root domain (e.g. kkhosravi.com), you must instead use an A record (which either maps to an IP or can be an Alias A record that maps the root domain to an AWS resource DNS, like an ELB or CloudFront Distribution DNS).

Answer

CNAME

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): [...] , Weighted, Latency, Geolocation, Failover, Mutlivalue Answer, and Geoproximity.

Answer

Simple

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): Simple, [...] , Latency, Geolocation, Failover, Mutlivalue Answer, and Geoproximity.

Answer

Weighted

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): Simple, Weighted, [...] , Geolocation, Failover, Mutlivalue Answer, and Geoproximity.

Answer

Latency

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): Simple, Weighted, Latency, [...] , Failover, Mutlivalue Answer, and Geoproximity.

Answer

Geolocation

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): Simple, Weighted, Latency, Geolocation, [...] , Mutlivalue Answer, and Geoproximity.

Answer

Failover

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you create a record (e.g. an A record), you can choose between the following 7 routing policies (which determines how Route53 responds to user's DNS queries): Simple, Weighted, Latency, Geolocation, Failover, [...] [...] , and Geoproximity.

Answer

Mutlivalue Answer

^^ Simple is mostly for a record that just has a single value (i.e. IP, AWS resource DNS) that you always map to
^^^ Wighted routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) proportionally based on a given number weight you assign each (e.g. 20, 30, 50)
^^^^ Latency routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the region (auto-detected in Route53 Record set GUI) that has least latency to the end user.
^^^^^ Geolocation routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on the continent or country of the end user (no matter what the latency).
^^^^^^ Failover routs traffic to multiple resources/IPs (defined in multiple record sets of same Name/Type) based on which record set is designated as Primary vs which is designated as the Secondary (The traffic always goes to the Primary, so long as health check passes, if health check fails, it failsover to secondary).
^^^^^^^ Mutlivalue Answer is similar to Simple, but you can have multiple record sets, each with a health check and the traffic goes to the value of any one of the records (chosen at random) that has a passed health check
^^^^^^^^ Geoproximity uses the proximity of the user and the resource is some wild ass combination that is defined in complex "Traffic Flows"

Question

In AWS, for Route 53, when you choose the [...] routing policy for your DNS record (e.g. A record), and you specify multiple values (e.g. multiple IPs) in same record (new line seperated), Route 53 will return the values to the user in a totally random order.

Answer

Simple

Question

In AWS, for Route 53, when you choose the [...] routing policy for your DNS records (i.e. you specifiy multpile A records with the same Name/Type but different values, e.g. different IPs), Route 53 will return the value to the user based on the number you assigned to the record (e.g. if you assign 20 to first record, 30 to second, and 50 to third, then user gets the value of first records 20% of the time).

Answer

Weighted

^^ note the weights are numbers that get added up and then distributed accordingly (e.g. 20 to first 30 to second, 50 to third, adds up to 100, so first record will get 20/100, i.e. 20% of the traffic.

Question

In AWS, for Route 53, when you have a non-simple routing policy, it is best to enable [...] [...] for each record set, so that if the underlying resource/server it points to is not reachable, the record is removed by Route53 and not considered in the routing policy (e.g. if you have a weighted routing policy for kkhosravi.com of 20% traffic to server A, 30% to server B, and 50% to server C, and server C is offline, 40% of traffic goes to server A and 60% to server B, and server C is not considered).

Answer

Health Checks

^^ you can create custom health checks (within the Route53 console) to point to specific path on the target server, e.g. /index.html, and then add that health check to the record set

Question

In AWS, for Route 53, when you choose the [...] routing policy for your DNS records (i.e. you specifiy multpile A records with the same Name/Type but different values, e.g. different EC2 or ELB DNS values), Route 53 will return the value to the user based on the shortest response time from user location to the region (auto-detected in the Route53 GUI when you choose this routing policy) where the target resource (e.g. EC2 instance, ELB) is located.

Answer

Latency

Question

In AWS, for Route 53, when you choose the [...] routing policy for your DNS records (i.e. you specifiy multpile A records with the same Name/Type but different values, e.g. different IPs), Route 53 will return to the user the value of the primary/active server IP if it is available (i.e if it passes configured health check), if not availble, if will return to the user the value of the secondary/passive server IP.

Answer

Failover

Question

In AWS, for Route 53, when you choose the [...] routing policy for your DNS records (i.e. you specifiy multpile A records with the same Name/Type but different values, e.g. different IPs), Route 53 will return to the user the value based on the user's location as configured in the routing policy of the record set, irregardless of the latency of the target server to the user (e.g. if record set A is configured for US users and record set B for EU users, if user is from US IP, they get routed to the value of record set A).

Answer

Geolocation

^^ you can pick geolocation either at continent level or country level.

Question

In AWS, for Route 53, when you choose the [...] [...] routing policy for your DNS records (i.e. you specifiy multpile A records with the same Name/Type but different values, e.g. different IPs), Route 53 will return to the user the value randomly (from among the values of the records that have passed their health check)

Answer

Multivalue Answer

^^ Multivalue Answer routing policy is similar to Simple routing policy, but with the addition that you can configure health checks for each record in the multivalue answer set