I think RAID 5 must be burried.

It was once introduced when magnetic disks where still very expensive and capacity limited, while at the same time there was a need for redundancy. Nowadays, disks are cheap and BIG. So big even that when a raid array is repairing there is a sizable chance of an random error occurring and all data will be lost.

Add to that the complexity of a the system and with it the sensitivity to errors and larger downtimes. And you will conclude that RAID5 is expensive and unreliable compared to other solutions such as RAID 10.

And really most database servers are fairly small and do not have fully time dedicated admins. This is especially true for such an accesible product as SQL Server. Why Microsoft claims that RAID 5 is popular with its customers is beyond me. They must be polling the large customers maybe, not the hundreds of thousands smaller ones.

At my company we had two times now a disk in a RAID 5 broke and the array could not restore itself and had to use backups to continue working on another server. An identical issue with RAID 10, never cause any issues or significant downtime.

Is there really ANY reason to go for RAID 5 today?

I think not.

As for the previously mentioned speed argument...think also about the limited use of a SSD to compensate the use of slower but larger magnetic disks. They are quickly becoming afordable and the performance shatters that of spinning media!