How many hard drives will you need?

Question

Hard disks

You need 10TB storage. RAID10 is used.
Here is an example:
To store 3 TB of data, you will need 5 hard drives of 600 GB each. Since it is critical for the system being developed to minimize read access time, we will combine two RAID 10 arrays that will work in parallel. You will need 15 more mirror disks, for a total of 20 disks.
Why so many discs? Why combine two RAID10 arrays? I don't quite understand.
Everywhere RAID calculators show that in order to provide the required volume, you need twice as much volume as planned.
It turns out that according to this scheme I will need 40 (wut) disks? Can I limit myself to 20?

Answer 1

Storage of what exactly? I can easily imagine a loaded 10TB DBMS (and a little over 20TB of raw storage capacity), which will not take off on the HDD at all just because of the access time requirements and all these 20TB are recruited by server SSDs.
And I can even more easily imagine a 10TB storage for backups, where the performance should just be sufficient in a reasonable time to put a new backup or read the one you need in case of an accident, for which raid5 or 6 is enough, or maybe even a couple of 10TB disks will turn out to be cheaper, you need to already look at the price.
First, the tasks, application limitations, limits for further expansion, the budget for the entire storage - and only then how many disks will need to be ordered.
To store 10TB of information, at least one drive is required (the task may say that the disk does not need to be backed up, this also happens). Everything else is chosen on a case-by-case basis.

Answer 2

500GB disks?))) Are you on a budget or just haven't seen the latest price lists? Server disks are already much larger in volume ...
For your TK you need 30-40 disks, are you serious or joking? The probability of failure catastrophically tends to 100% !!)))
And doesn’t a hole cost you anything?...
Take 4 x 6Tb and you will have chocolate...

Answer 3

Raid ten is four disks, two in raid 1 mirror and on top of them raid 0 stripe
In general, you should think about buying more screws and changing the type of raid