Performance Limits And Pitfalls
Let’s cover a few things that must be considered when planning a transition to SSDs. We've already mentioned issues with sustained performance in prior SSD articles. This was an issue with older drive generations but has been improving over time. Still, you should take precautions. Most of the following items are valid for client PCs as well as for business and enterprise deployments.
Technically, all SATA drives can be utilized in RAID arrays using suitable controllers. However, some products don't deliver expected performance in RAID configurations. This is often a firmware issue, but should be checked nonetheless before investing in specific SSD products. Sometimes the TRIM feature (see below) won’t work on RAID configurations due to incomplete AHCI support.
Hard drives should be defragmented on a regular basis to make sure that frequently-used files are available on the faster sectors and that larger files aren’t unnecessarily scattered across the hard drive, which increases the time needed to retrieve them. Hard drives need to read and write sequentially as often as possible because head physical movements introduce latency. This isn't a problem for SSDs since data is always distributed by the SSD controller all over the drive. This is normal. Applying defragmentation tools to SSDs will be counter-productive, wearing down flash cells without introducing any advantage. Hence you should switch defrag off.
The TRIM feature is used by the operating system to inform the SSDs about blocks that were deleted and are available for new data. This allows SSDs to optimize writes in a way that maintains maximum write performance and optimizes wear leveling. SSDs do this internally, but the process is more efficient when triggered by the file-aware operating system. TRIM requires support in both the SSD’s firmware and the operating system. Drivers and the storage controller must support AHCI, as well. This often means using Windows 7 or Windows Server 2008 R2, Linux kernel 2.6.33, or FreeBSD 9. All older system versions will not support TRIM, which can result in severely limited write performance. However, TRIM support is complex, so double check that support is possible and enabled.
TRIM is supported by Intel SSDs with firmware 02HA and up, Indilinx 1819 and up, all JMicron 612 and 618 devices, Marvell hardware with firmware 0002, all SandForce devices, Samsung’s VBM19C1Q firmware for PB22 drives, and all Samsung 470 SSDs. The tool Crystal Disk Info provides great help with firmware and SSD checking.