I have a Sandisk Extreme Pro 240GB, and I want to mount it on my iMac mid 2011, with Yosemite OS. My question is if I need to activate TRIM, or not.
Apple made some changes that prevent the third party tools from being able to enable TRIM for third party SSD. You can do it but apparently you need to make some changes that may open you to potential security issues. See the article below for more info.
http://www.macworld.com/article/2849366/mac-wont-boot-about-yosemite-and-your-third-party-ssd.html
The newer Mac’s like my Macbook Pro use a PCI-Express SSD so TRIM doesn’t even make sense
PCI-Express SSDs are not SATA so TRIM is not usually supported. However some of the PCI-Express SSD vendors are aware of TRIM and may be able to support it with their driver.
The companies that actually make the SSD’s have a better idea of what is going on inside their drives IMO and should take care of TRIM. Even though SSD’s have been around a while now they aren’t as mature technology as traditional mechanical drives.
That’s why newer SSD’s are moving the job of TRIM back to the SSD drive where it should be IMO!
“The unique driver and firmware also allow the RevoDrive 350 to support TRIM, SMART, and secure erase while typical RAID controllers do not allow those features.”
http://www.anandtech.com/show/8430/pcie-ssd-faceoff-samsung-xp941-128gb-256gb-and-ocz-revodrive-350-480gb-reviewed
The biggest argument I have against enabling TRIM is that TRIM is a SATA command.
What if the SSD is connected via PCIe, USB 3.0, FireWire, or Thunderbolt - such as on Macs or PCs. The Mac won’t even recognize the drive as an SSD. Enabling TRIM would be USELESS for SSDs connected these other ways anyways!
Not to mention they might just be moving to NVMe as Windows 8 already has native support for it.
While Advanced Host Controller Interface (AHCI) interface has the benefit of legacy software compatibility, it does not deliver optimal performance when an SSD is connected via PCI Express bus. This is because AHCI was developed back at the time when the purpose of a host bus adapter (HBA) in a system was to connect the CPU/memory subsystem with a much slower storage subsystem based on rotating magnetic media. Such an interface has some inherent inefficiencies when applied to SSD devices, which behave much more like DRAM than like spinning media.[1]
NVMe has been designed from the ground up, capitalizing on the low latency and parallelism of PCI Express SSDs, and fulfilling the parallelism of contemporary CPUs, platforms and applications. At a high level, the basic advantages of NVMe over AHCI relate to its ability to exploit parallelism in host hardware and software, manifested by differences in depth of command queues, interrupts processing, the number of uncacheable register accesses etc., resulting in various performance improvement
