This is a short fix for the error FAIL(S0150) that comes up during the HP Vertica Installation.
HP Vertica requires that I/O Scheduling be set to deadline or noop.
What are the IO scheduling types :
Input/output (I/O) scheduling is the method that computer operating systems use to decide which order block I/O operations will be submitted to storage volumes.
I/O schedulers can have many purposes depending on the goal of the I/O scheduler. Some common ones are:
To minimize time wasted by hard disk seeks
To prioritize a certain processes' I/O requests
To give a share of the disk bandwidth to each running process
To guarantee that certain requests will be issued before a particular deadline
Types of scheduling
First In, First Out (FIFO), also known as First Come First Served (FCFS)
Last In, First Out (LIFO)
Shortest seek first, also known as Shortest Seek / Service Time First (SSTF)
Elevator algorithm, also known as SCAN (including its variants, C-SCAN, LOOK, and C-LOOK)
N-Step-SCAN SCAN of N records at a time
FSCAN, N-Step-SCAN where N equals queue size at start of the SCAN cycle
Completely Fair Queuing (CFQ) on Linux
We are not going to explain all of them, we will only talk about the ones that HP Vertica recommend using and why.
There two are deadline and noop.
-The Deadline scheduler gives priority to read requests over write requests. It also imposes a deadline on all requests. After reaching the deadline, such requests gain priority over all other requests. This scheduling methods helps prevent processes from becoming starved for I/O access.
-The NOOP scheduler inserts all incoming I/O requests into a simple FIFO queue and implements request merging. This scheduler is useful when it has been determined that the host should not attempt to re-order requests based on the sector numbers contained therein. In other words, the scheduler assumes that the host is definitively unaware of how to productively re-order requests.
This scheduler is best used on solid state drives (SSDs). Since SSDs do not have a physical read head, no performance penalty exists when accessing non-adjacent sectors.
Let's go an see how we can fix this erros
HP Vertica requires that IO scheduler be set to deadline or noop
Viewing the contents of the /sys/block//queue/scheduler file to see you actual schedule definition.
In my case the devices that are going to be used for the HP Vertica install is sda.
To it's definition :
To change the scheduler, write the name of the scheduler you want the device to use to its scheduler file. You must have root privileges to write to this file. For example, to set the sda drive to use the deadline scheduler, run the following command as root: