SRE Interview Questions 2

*) What is wrong with the output of iostat?

     It will be nicer to see the output in terms of bytes rather then in terms of block.

*) Is static or dynamic linking better?  Explain?

     As far as know its depends, when I use the command “ldd” in redhat linux with in executable file its shows few shared library information. From there what I can say is, if we have lots of executable in an application group and mostly if they get installed as a group for the dependency then a dynamic linking will be better, with in those executable group and if the owner of the application don’t want to be dependent with other then he can choose the static linker.

*) What is the difference in failure modes between RAID10 and RAID 0+1?

     RAID 10 mean, 1st it do a mirror group with and then that that mirror group and do strip. [ I mean Disk D1 and MD1 in one group and Disk D2 and MD2 in other group and the data stored from D1 then to D2 and on the back ground MD1 mirrored the D1 data and MD2 mirrored the D2 data] The good thing about this is if any of the disk from [ D1 or D2 ] failed or from [MD1 or MD2 ] failed still we can get the data back.   

RAID0+1 mean, 1st it do the strip and then mirror the striped disks on the mirror disk group. over here if any of single disk get failed [ from original strip group or the mirror group of that strip data, then we will not be able to get the data back, I personally don’t suggest this. ]

*) How do you catch SIGKILL?

     As far as I know we can’t catch SIGKILL [ kill -9 PID ]

*) There is a directory with lots of files inside and you have all the permission and there is nothing such immutable permission set, if you are going into that directory and trying to delete you can able to delete, but you are not able to delete the directory, why?

     When OS try to delete the directory to delete its files, the inode number are so much that the kernel memory space is getting filled up and that's the reason its not able to delete. Few time you might get the error like " Too many parameter passed " and the way you can delete that is " ls | xargs rm -rf "

*) What is the major effect on routing of configuring your routers with the ‘no ip classless’ command?

*) How do you debug a catatonic system?

*) What are the disadvantages of centralized configuration management?

*) What is great about ZFS? Explain?

*) How can you optimize performance of a volume on a SAN?

*) How does NFS performance vary with the number of files in a directory?

*) What can contribute to latency measured with ping?

*) What is the best MTA?  Explain?

*) What command causes the most problems on a UNIX system?  Explain?