Which RAID type to choose for the server?

Question

RAID

No matter how much I tried to understand this issue, I still lack experience.
The task is set - to collect a copy of the server, which is already available. I didn't collect it.
At this stage, there are 3 SSDs that are twisted in RAID1. I
contacted the technical director, he explained that this was done for security purposes, since if one disk falls off, you can not bathe for some more time, plus replication will be faster.
From my point of view, 3 disks in RAID1 means that there is 33% of useful information on it, while it is not clear how exactly replication will be performed if one of the disks fails. If the reading is from two, then a mismatch is possible (a primitive example - somewhere 0 will fall out, somewhere - 1, where to write from?)
Considered RAID5 - those. dir says that this option is worse, since a lot of IO will be spent on disk recovery, which is very steamy. On the other hand, my thoughts say that this is an SSD and not so critical.
In general, help to understand. You can even in VK\Skype

Answer 1

First you need to define a task.
If the task is maximum fault tolerance, then you need a sixth raid.
If you need performance - the tenth.
If you want to save on matches - the fifth.
If you need at least some kind of reservation - a mirror. Fencing a mirror and one spare is a strange choice, but possibly justified, for example, if you have critical data there and there is a risk of losing it (but to be honest, practice shows that there is a chance to lose the second medium while the spare is being rebuilt).
SSDs are also different, they are reliable (Intel, for example), they are affordable (OCZ, for example). It all depends on what data you have on them and how much you are willing to pay. If these are temporary profile folders on a terminal farm - this is one thing, if your production database is from CRM \ ERP - another (in the latter case, pure ssd storage should be skeptical).

Answer 2

RAID-5
RAID-1
RAID-10
any of these are all good.
SSD recommend https://www.crucial.com/

Answer 3

I advise you to add +1 SSD:
RAID 5 - at least 4 disks, it still doesn't work very well on three.
RAID 10 - also 4 drives - a balance between speed, capacity and security

Answer 4

The task is set - to collect a copy of the server, which is already available. I didn't collect it.
At this stage, there are 3 SSDs that are twisted into RAID1

you are tasked with making a copy of the server. For any problem that arises in the future when moving away from the "technical task", the demand will be from you.

Answer 5

1. What is a RAID array used for?
to improve:
1. Productivity. Ask a question - how loaded will the system be, how important is its performance?
2. Fault tolerance, which includes the speed of recovery after a failure. Ask the question - how critical is downtime in case of failure? + Is it acceptable to reduce the quality of service (provided by the server) in the process of recovery after a failure?.
To back up information, only backup to external devices should be considered, because. any RAID array does not close this issue and does not reduce the risk of information loss.
We set priorities in accordance with paragraph 1, choose in accordance with the schedule:

Answer 6

Are you running out of space or what? In terms of high availability, raid 1 is better, well, raid 5 is generally better to never use.