RAID "Hard Drive" Calculator

Personally i would not waste my time with 1GB hard drives.  You will certainly have failures soon after configuring. 1GB HD have not been available for a long time, and as they fail you will be replacing them with much larger drives,.  But only getting 1GB from them.

My two cents

RAID 50 is a RAID 5 over a RAID 0, so a RAID 5 you get X-1 drives of storage.  In order to do a RAID 0 you need 2 storage units.  So, divide the total number of drives you are using in your array by 2 and then subtract 1 from that and you'll get your useable.  RAID 60 would just be divide by 2 and subtract 2.

I agree with pjam.

Lots of RAID options, lots of reasons to go with various flavors.  I don't think you really need a calculator to figure out the size as it's a pretty simple process.

My additional two cents :)

Sounds like a homework question to me.
Nobody uses 1 gigs anymore.

Another thing to note is that it also depends on the RAID controller AND the file system you put on the resulting array.

LOL, oops...My previous calculation was for a RAID 51 and 61.  

RAID 50 is Number of drives = X, Amount of useable storage units = X-2.
RAID 51 is Number of drives = X, Amount of useable storage units = (X-2)/2
* One parity drive per array - so you lose 1 drive of space per array for redundancy

60 is X-4
61 is (X-4)/2
* Two parity drives per array - so you lose 2 drives of space per drive for redundancy

@mrfreshly - where did you get this from "RAID 50 is a RAID 5 over a RAID 0" RAID50 is striped RAID-5, not the other way round - i had trouble trying to visualise Stripes that are then collected into a RAID-5.

@finance - You are correct, 22 spindles split into two RAID-5 sets of 11 1GB spindles each, giving 10GB of useable (each) therefore 20GB in total.

As the others said 1GB drives are really really old (probably 20 years old), did you mean 1TB?

@PGM - suspicions aroused!

Did you actually try the calculator they listed Gerald? Whether or not 1GB drives were ever available and whether or not it's homework the fact is that it's the first one listed on Google for "RAID 50 calculator" yet it gets it wrong - try 27 disks in the array. Second on Google gets it wrong too, 3rd doesn't do RAID 50, 4th works properly, 5th one gets it wrong. Most of them don't seem to understand that there can be more than two RAID 5s in the stripe.

@andy - No, why would i want to use somebody else's calculator when i know how to do it (well i think i do anyway) :-)

@mrfreshly - i know how to configure RAIDsets, i was commenting on your use of language, in your first post you said "RAID 50 is a RAID 5 over a RAID 0" which seems to say that RAID50 is a a set of Stripes that have been RAID-5'd, instead of the other way round.

We already have the ambiguity of RAID0+1 and RAID1+0, both having been defined by different vendors as Striped-Mirrors and Mirrored-Stripes.

I want to deprecate those two terms in favour of RAID10 which most people define as Striped-Mirrors, except for this reference (see bottom of page 4) i found on the Dell website saying the opposite.

@gerald - sorry for the wording confusion...need more coffee. :)  My explanation was more for the original post, only partly for you.

Hmm, you have enough spare time to find errors in Dell white papers, I have enough spare time to find errors in RAID calculators ;)

Does that make us both sad geeks?

From the accepted solution... "RAID systems are designed for fault tolerance. 3 to 6 drives is a good number."

That's only correct for un-nested RAID levels such as RAID 5, it is not correct for nested RAID levels such as RAID 10, 50 and 60. HP EVAs for example may have over 100 disks in a RAID 50 configuration although there's a little bit more than basic RAID 50 going on there so they call it vRAID 5 but apart from some space being reserved for distributed spares it is still RAID 50 under the hood.