How many disks does RAID One require?

Question

I am having an issue with the trigger below. I am using SQLDeveloperx86 Build 15.21 (v4.0.2.15). The compiler log gives me the error shown in this posts header. Consequently I cant use the trigger as a result. The squiggle line of death appears under the "/" symbol

create or replace trigger clientexists
        after insert on DISPATCH
        for each row
        declare 
          countRows Integer;
          begin
            select count(*) into countRows from CLIENT
            where CLIENT.name = DISPATCH.client;
            if countRows = 0 then
                  insert into CLIENT
                  values(:new.client,NULL,NULL,NULL);
            end if;
        end;
        /
        show error

Solution

A RAID 1 creates an exact copy (or mirror) of a set of data on two or more disks, so you need at least 2 disks. You can read this for more.

Comments

[hjpotter92]

You need to set the delimiter to / before creating trigger.

[user4021524]

Sorry can you elaborate on that, as far as I know I didn't need to set anything in regards to the slash before.

[a_horse_with_no_name]

What does show error return?

[AndreDuarte]

You probably have an SQL error in your trigger. Did you checked it?

[Alex Poole]

Are you compiling this from the SQL Worksheet, in which case it looks fine; or from the code editor window (for an existing trigger, or from choosing table->trigger->create)? The / and show errors should be omitted from the code editor, and you would get the red squiggle there.

[Ƭᴇcʜιᴇ007]

RAID 1 also requires an even amount of drives. If you want to use an odd number (like 3 drives) you need RAID 1E.

[Naidim]

I think it would be wasteful to use it with any more than two drives, as you lose half your storage space. Using a parity level like RAID-5 would be better, or RAID10 (or RAID0+1), which gives you speed as well as mirroring.

[Xantec]

while I'm sure it depends on the raid controller, you might use Raid1 with >2 disks (over Raid5/10/0+1) if you were worried about being able to access the data in the event that you lose the raid controller (ex: HW failure + no replacement)

[jack]

So harddrives and two other hard drives?

[Greg Jennings]

Yes, one harddrive (source) and two other harddrives to be used for RAID 1.

[user4021524]

Thank you very much for that Alex, it is obvious I am a little confused about this :new command then. I will research this further, do you have any good material on the subject?

[Alex Poole]

@user4021524 - the documentation on correlation names is a good place to start.