Server SSDs in RAID 1: Software or Hardware RAID

Hello

I would recommend against options 1 and 2. If you are going to invest the money into SSDs then don't bottleneck the performance by using driver or software RAID.

The S100/S110 are driver based RAID controllers. They are firmware running on the system board within the chipset. They do not have their own resources so they use the system's resources. RAID controllers that do not have their own processors or memory are considered driver based RAID controllers.

RAID arrays that you create through software or operating systems are software based RAID. All of their functions are done through the operating system. They also use system resources because they do not have their own.

Hardware RAID controllers have their own processors, and some have their own memory. They do not borrow resources from the system. You will get your best performance from a hardware RAID controller like the PERC H710.

Add a PERC hardware RAID card and use that to mirror the SSDs. Won't this prevent TRIM commands from passing to the SSDs? Is TRIM even necessary with todays SSDs?

When you use a chipset/driver based RAID controller or a hardware controller then TRIM is not necessary. If the controller supports SSDs then it has some method to let the drive know the block is unused. The operating system does not have direct communication with the drive, so the RAID controller handles that type of operation.

Let me do some tests for you real quick to show you the differences between the different technologies:

All tests were performed by copying a very large ISO file from location to another on the same drive. All drives tested are 6Gb/s, but not all of the controllers support that speed. The PERC 5/i is a 3Gb/s controller.

My home computer(Top of the line) using a chipset/driver based RAID controller
Copying 7200 RPM HDD - Started out at around 200MB/s, but quickly dropped down and stabilized at around 40MB/s.
Copying Samsung 840 EVO(250GB version) - Started out very fast ~1.2GB/s, but dropped quickly and stabilized around 275MB/s.

Home server running PERC 5/i(Uses exact same 7200 RPM drives as my desktop)
Copying 7200 RPM HDD - started out ~350MB/s and quickly dropped down and stabilized at around 90MB/s.
I also tested with write cache disabled. It was incredibly slow. The speed stabilized at around 4MB/s, but that is mainly because it is RAID 5. If it were a non-parity array the performance hit would not have been as dramatic. This goes to show that you should never run a parity array on a controller without write cache.

My lab server at work using an H710P
7200 RPM HDD(RAID 5) - Started out slow ~40MB/s, but stabilized at around 105MB/s.
7200 RPM HDD(RAID 1) - 1.65GB/s. It completed the copy before it had time to stabilize. It was a 6GB ISO that completed in about 3 seconds. I copied an entire folder of ISOs and the speeds were all over the place, but it was well over 400MB/s most of the time.

The SSDs will be faster than the 7200 RPM SATA drives no matter what your configuration is, but you will be missing out on their potential if you use anything other than a hardware RAID controller that has cache.

Thanks

Hardware controllers are generally unaware of FS data usage bitmap. So there is generally NO TRIM.

Theoretically OS-issued Trim command can be translated to drives. But this requires some computation and can reduce reliability. So only some softraids implement TRIM, Like intel, only in RAID0 performance mode.