HP PCIe IO Accelerators for ProLiant Servers - Manual (Page 108)

Using Windows page files with the IO Accelerator 108
Using Windows page files with the IO
Accelerator
Introduction to Windows page files
This section describes how to effectively use paging (swap) files on IO Accelerator devices with
Windows® operating systems.
Using a page file with a traditional disk drive places practical limits on the usable size of the page file
and virtual memory due to the poor performance of disk drives in relation to RAM. Placing the operating
system paging file on one or more IO Accelerators enables much larger page files and usable virtual
memory. This is due to the much faster response times and bandwidth on IO Accelerators versus hard
disks. IO Accelerator software prior to version 2.0.2 does not support paging files.
Configuring IO Accelerator paging support
The IO Accelerator 2.0.2 driver and later versions can be configured to support paging files on one or
more IO Accelerators. Configuring paging support requires that each IO Accelerator used with a paging
file preallocates the worst-case amount of memory it might need in any possible I/O scenario. Memory is
pre-allocated on a per-adapter (ioDIMM) instance.
Because of the extra host RAM memory use, paging must be enabled only on IO Accelerators that
actually hold a paging file. You can place a single paging file on more than one IO Accelerator.
Windows® operating systems stripe paging I/O across all available paging files, providing additional
performance to the VM subsystem.
RAM consumption
The amount of RAM preallocated per IO Accelerator depends on the total size of the device and the
sector (block) size selected when formatting the drive (with fio-format). The following table lists the
estimated memory consumption for the various device and sector sizes.
IO Accelerator size (GB) 512 byte sector 4096 byte sector
80 2,278 284
160 4,556 569
320 9,132 1,141
640 18,264 2,282
Host RAM Consumption in Mebibytes (MiB); 1024 x 1024 = 1 MiB
Using a larger sector size significantly reduces the amount of host memory consumption needed for
paging support. HP recommends using a 4K sector size be used because:
• that is generally the natural size of a host memory page, and