13 June 2017

8 Selected interview Questions for Quick revision

AWS Interview Questions
AWS Interview Questions
Q1. Explain Elastic Block Storage? What type of performance can you expect? How do you back it up? How do you improve performance?
A1. EBS is a virtualized SAN or storage area network. That means it is RAID storage to start with so it’s redundant and fault tolerant. If disks die in that RAID you don’t lose data. Great! It is also virtualized, so you can provision and allocate storage, and attach it to your server with various API calls. No calling the storage expert and asking him or her to run specialized commands from the hardware vendor.
Performance on EBS can exhibit variability. That is it can go above the SLA performance level, then drop below it. The SLA provides you with an average disk I/O rate you can expect. This can frustrate some folks especially performance experts who expect reliable and consistent disk throughput on a server. Traditional physically hosted servers behave that way. Virtual AWS instances do not.
Backup EBS volumes by using the snapshot facility via API call or via a GUI interface like elasticfox. Improve performance by using Linux software raid and striping across four volumes.
Q2. What is S3? What is it used for? Should encryption be used?
A2. S3 stands for Simple Storage Service. You can think of it like ftp storage, where you can move files to and from there, but not mount it like a file system. AWS automatically puts your snapshots there, as well as AMIs there. Encryption should be considered for sensitive data, as S3 is a proprietary technology developed by Amazon themselves, and as yet unproven vis-a-vis a security standpoint.
Q3. What is an AMI? How do I build one?
A3. AMI stands for Amazon Machine Image. It is effectively a snapshot of the root file system. Commodity hardware servers have a bios that points the the master boot record of the first block on a disk. A disk image though can sit anywhere physically on a disk, so Linux can boot from an arbitrary location on the EBS storage network.
Build a new AMI by first spinning up and instance from a trusted AMI. Then adding packages and components as required. Be wary of putting sensitive data onto an AMI. For instance your access credentials should be added to an instance after spinup. With a database, mount an outside volume that holds your MySQL data after spinup as well.
Q4. Can I vertically scale an Amazon instance? How?
A4. Yes. This is an incredible feature of AWS and cloud virtualization. Spinup a new larger instance than the one you are currently running. Pause that instance and detach the root ebs volume from this server and discard. Then stop your live instance, detach its root volume. Note the unique device ID and attach that root volume to your new server. And the start it again. Voila you have scaled vertically in-place!! Read online for more questions

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