Resilience Flashcards
In the realm of IT/Networking/Security what is redundancy?
Redundancy is simply the duplication of parts of a system so that it is always up and running, as a protection against pieces of a system failing. Whether it is redundancy in an office building, an enterprise, or across multiple countries.
What is geographic dispersal?
This would be spreading out your datacenters and resources across multiple geographic locations in case of widespread failure in one location (like from a tornado, hurricane, etc)
What is multipath i/o?
Multipath input/output is the practice of making multiple paths for data to flow through a network if one piece were to fail.
Such as having multiple switches set up and if one were to fail, the traffic meant for that path would be re-routed to another path.
What is RAID?
Redundant array of independent disks
A way of creating redundancy in storage on drives, there are multiple redundant drives that run in tandem with each other, holding some or all of the data from the others. So if one fails, things still keep going.
A user would not notice any change if one of the drives were to fail.
But behind the scenes a system administrator will go in and replace the failed drive.
What is load balancing?
Load balancing is a practice that involves having both online and offline servers(waiting to be turned on) and a load balancer that decides which servers that traffic will flow to, in an attempt to keep things evenly balanced.
The load balancer keeps in constant contact with all of the servers to check on how they are doing, if any of them don’t respond the load balancer might load up one of the servers on standby to use as a replacement.
What is nic teaming? Or LBFO?
Nic teaming or Load Balancing/Fail over is a way of performing load balancing without a load balancing device, and instead using multiple NICs. Multiple NICs will all be used in tandem, integrated with a switch and the server so that they both understand what is going on. The NICs will talk to each other and perform periodic check ins, and if one of them doesn’t reply, operations will be transferred to another NIC on standby.
What is a UPS?
Uninterruptible power supply.
A way of getting Short term backup power in case of surges,blackouts,brownouts, etc.
An offline/standby UPS will be off while everything is going normally, and once power is off for whatever reason there will be a short time frame where power is lost, and then power will be switched to the UPS.
A line-interactive UPS will pick up the slack in power supply if there is wavering or inconsistent power happening.
An on-line/Double conversion UPS is the most expensive and complicated, it will always be online, and there will no outage whatsoever if power gets cut because it is always on and running.
What is a PDU?
Power Distribution Unit
Basically a power strip but smarter.
Usually in a server rack.
Often include monitoring and control functions.
What is SAN?
Storage area networks(SANs) are a specialized high performance network of storage devices, allowing you to store data between different devices, or even from one datacenter to another, over a network.
Unlike a NAS if you need to make changes to a file stored on a SAN you only need to change that portion, rather than rewriting the entire file.
Very efficient at reading and writing.
You can use it for SAN-to-SAN replication, which would be duplicating data from one datacenter to another, or you can take a SAN snapshot and create a state of data based on a point in time, and copy that data to other SANs.
What is VM replication.
Maintaining a single VM and replicating it to all others.
A VM is really just one big file.
It offers constant service offering anywhere in the world.
You can also recover from a replicated copy and it acts as a backup.
What is the difference between a full backup and an incremental backup?
A full backup backs up literally everything on a machine, you will want this one first.
An incremental backup will only back up all files that have changed since the last incremental backup. A recovery from incremental backups will require both the last full backup, and all incremental backups that have occurred since.
A differential backup is a bit different, it backs up all files that have changed since the last FULL backup. Thi A recovery from differential backups will require both the last full backup and the most RECENT differential backup.
What is an archive attribute or an archive bit on a file?
An archive bit is a single bit within a file that determines if it has been backed up yet or not.
How long do Full/Incremental/Differential backups take to backup and restore comparatively?
A full backup is going to take a long time to backup, but a low time to restore.
A backup using incremental backups is going to take a low time to back up each time, but a long time to restore since you need to restore from all of these different backups together and the last full backup.
A backup using differential backups is going to take a medium time to back up each time since it keeps growing larger and larger, and a medium time to restore since you only have a maximum of two backups you need to restore to a system.
What is NAS?
Network attached storage.
A large storage array that is connected over a network.
Also referred to as file-level access, because if you need to make changes to a file stored on a NAS you have to re-write the ENTIRE file on that device.
In regards to restoring an application instance and order of restoration, what typically would be the first thing you should restore while putting it all back together?
Databases.
