4Kn SAS drives

Thanks guys but most of the questions were missed. The specific case I am looking at is server storage behind a RAID controller. Entry level. That rules out SSD because of TRIM. The specific controller is a (Adaptec) 8405.

I have yet to see a RAID controller that supports TRIM. If you know of one please advise.

The PERC5/6 is not a simple pass through in terms of TRIM. The only "controllers" capable of doing TRIM are the Intel motherboard controllers with the Series 8 chip-set or newer and even then will only work in RAID 0 or 1.  

   Kevin to be honest I did the same thing you did. I used some consumer SSDs in a RAID 5 configuration behind a Adaptec 8405. The two major warning I heard was 1) Sooner or later the IO will come to its knees because TRIM isn't supported but I too, in my limited knowledge of TRIM, figured worst case it would simply be re-writing a bunch of cells. 2) Unless you use the Enterprise SSDs you would hit a problem where loss of power would corrupt the cache. I figured like a battery cache on a RAID controller a good APC battery backup with shutdown would more or less solve that problem. So I even took more of a chance and used consumer SSDs. It has been over a year and no issues. My problem is that doing something that isn't recommend, in a server no less, kind of bothers me. I figure the safer bet would by going back to platters. Hence the question.

   Thanks Phillip. You have been the only one to answer my questions :) #3 is still bothering me. I understand application and OS compatibility between 512n and 4Kn buy why bother with 512e? What not just stick with 512n?

A battery on the RAID controller isn't really related in any way to the cache on any drice SSD or otherwise. All of these "Power Loss Capacitors" and "RAID Battery Cache Backups" are insurance and as in real life you can easily purchase too

   We are looping back around to the original question. "Enterprise" SSDs  and SAS SSDs are way to expensive for entry level servers. 15K RPM SAS drives lack capacity. I put consumer SSDs in a small server and have been very impressed so far but know that I am doing something that is not generally a good idea hence the move back to platters. It just seems like the 3.5" 7200RPM SAS drives make the most sense. Can't see going SATA.

   That is interesting about the 512e. Didn't see how it benefited the end user. Guess it doesn't :)

Thanks guys. Very informative information.