HP PCIe IO Accelerators for ProLiant Servers - Manual (Page 105)

Trim support (Windows only) 105
Trim support (Windows only)
Introduction to Trim
Trim is used to address a unique property of solid state drives. The issue occurs when a user deletes a file,
and then the drive that contains the file does not recognize that it can reclaim that space. Instead, the
drive reads the data as valid until the system informs the drive it can overwrite that data. With a typical
hard drive you can continually write to the same sector of the drive without significant degradation.
However, a solid state drive writes to different flash memory areas when the same logical sector is written
to.
Because of the way flash memory handles writes, having a full SSD can cause significant reduction in
write throughput. Currently available storage stacks and file systems were not designed with this caveat in
mind. The SSD software must assume that all sectors contain valid data, and therefore treat the drive as
full. In reality, a file system does not normally contain a full drive of data.
Trim is an enhancement to existing file systems that informs the SSD software of logical sectors that do not
contain valid user data. Trim retrieves this information from a file system when a file has been deleted,
and it informs the drive that it can reclaim the space held by that file. This feature enables the wear-
leveling software to reclaim that space as reserve to handle future write operations.
For Trim to perform this task, it continually runs in the background and monitors the file systems being
used on IO Accelerator devices. The process is meant to run in the background so as not to noticeably
impact the performance of the computer.
Trim platforms
The Trim feature is available on IO Accelerators for Windows® operating systems starting with
Windows® XP and Windows Server® 2003.
NOTE: Starting with Windows® 7 and Windows Server® 2008 R2, Trim capabilities are built
into the operating system. IO Accelerators support Windows® 7 Trim, which means that IO
Accelerator Trim is unnecessary under Windows® 7 and Windows Server® 2008 R2, and it
will not run when either of these is present. No system changes are needed. The IO
Accelerator Trim service automatically shuts off if it is attempting to run on a Windows® 7 or
Windows Server® 2008 R2 or later operating system.
Using Trim
Trim runs quietly in the background as a Windows® Service a few minutes after the computer is started,
so as not to slow down the boot process. However, you can also fine-tune Trim by using the configurable
settings.