Raid Controller and SSD drives

You appear to be talking about RAID1. In that system, all the data are written to TWO places (separate drive units) simultaneously. If either of them fails individually, the system can alert you to that failure and keep on running from the remaining good unit until you can replace the failed unit. Then it can restore the RAID array by copying all data from the remaining good unit to the new replacement.

RAID1 is ideal for applications where users cannot tolerate significant downtime during normal operations, but some scheduled downtime for repairs is acceptable at other times. For example, I use a RAID1 system in Point-of-Sale application in our retail store where computer failure would be a major disruption. But any repairs can be done when the store is closed.

RAID1 is NOT! a backup system! If any actions - mistakes by operators, bad incoming data, malware, etc. - write faulty data or delete data from the RAID1 array, it happens to BOTH disks simultaneously and there is NO un-corrupted data to recover. Of course, if both disk units suffer failures, or if the computer or its RAID controller subsytem fail, you lose access to the data and MAY not be able to re-access it. Your posts suggest your main concern is complete loss of data from a "crash". RAID1 does not give you sufficient protection from failures of that type. For that you need a proper BACKUP system and procedures, not RAID1. For example, I worked in a large facility with professional data centre management that experienced a failure of their RAID5 array. Now that is a RAID variety that can keep running and rebuild itself automatically during normal operations when one of the member disk units fails and is replaced. This particular system experienced TWO disk unit failures, and could not rebuild itself. After the failed units were replaced, the entire data set had to be restored from BACKUPS. The staff had TWO backup systems in use - one stored on-site, one stored off-site - so the restore could be done with VERY little loss of data from a portion of the last day before the failure. I know another similar business whose data centre was in a basement location (relatively common, oddly) that was flooded. For them, on-site storage of backups might have been a disaster!

So, review your real requirements and, if appropriate, look into proper data backup systems.

IF you need RAID in whatever flavour, examine your Dell PowerEdge 900 system carefully. My look at their website says that unit comes with a Dell PERC 6i SAS 6/iR or PERC 6/E RAID controller and management system capable of a LOT of good RAID work. To some extent the exact details depend on the specific model number of your PowerEdge 900 system and of the particular RAID controller system it has. But one important feature is this. That computer system is designed to allow you to use a variety of Operating Systems. Usually when you use a RAID controller and management system the device drivers and the software versions depend on what OS is in use. The Dell system HAS those drivers and utilities included, making it much easier to use for most applications of that system.