This document shows the terms and definitions that are specific to the configuration of the cache task.
Read-data: Data read from disk.
Write-data: Data to be written to disk.
Memory Overhead: Additional physical memory cost of running cache. If you see the memory overhead is large, you may cut it down by using a bigger block size.
Storage Overhead: Additional level-2 storage cost of running cache when level-2 cache is enabled.
Level-1 (L1) Cache: Also known as RAM Cache. It uses physical memory as a cache medium. The memory can be OS Managed Memory and/or OS Invisible Memory as described below. You can manually enter the amount of system memory or Invisible Memory to use for the L1 cache. A value of 0 means disabled.
Advanced Level-1 Cache Options:
Individual Read/Write Cache Space: When this option is checked, the level-1 cache space will be divided into two separate areas according to the specified ratio, which are dedicated to read cache and write cache respectively. 100% Read means that the whole cache space is used for caching read-data only, while 100% write means caching write-data only. If this option is not checked, the whole level-1 cache space is shared by both reading and writing. >> more
Release L1 Cache on Hybrid-Sleep or Hibernation: Upon hybrid-sleep or hibernation, Windows saves RAM contents to a disk. As level-1 cache is made of RAM, its cache contents are also saved to disk, leading to the increment of process time. This option is to remove level-1 cache (MM) contents upon hybrid-sleep or hibernation in order to not affect the sleep/hibernation process time.
Note: Cache contents in Invisible Memory are always removed upon hybrid-sleep or hibernation whether this option is enabled or not.
Keep L1 Cache on Fast Shutdown: This option is to maintain the cache contents of level-1 cache (MM) across the shutdown (not Restart) and the next boot. However, it will increase the shutdown/boot time. The option is available in Windows 8 or above and effective with Windows Fast Startup feature turned on.
Note: Cache contents in Invisible Memory are always removed upon shutdown whether this option is enabled or not.
Level-2 (L2) Cache: Also known as SSD cache, use SSD, flash disk or other faster persistent storage device as cache to speed up traditional mechanical disks. Unlike level-1 cache, cache contents stored in level-2 cache are persistent across computer restarts. See Level-2 Cache.
Level-2 Storage: A partition formatted to store cache index and content for level-2 cache. It is not visible and recognized by the operating system. Each level-2 storage volume can provide cache storage for multiple (no more than 16) cache tasks. See Manage Level-2 Storage.
Advanced Level-2 Cache Options:
Individual Read/Write Cache Space: When this option is checked, the level-2 cache space will be divided into two separate areas according to the specified ratio, which are dedicated to read cache and write cache respectively. 100% Read means that the whole cache space is used for caching read-data only, while 100% write means caching write-data only. If this option is not checked, the whole level-2 cache space is shared by both reading and writing. >> more
Gather Interval: Specifies a recurring interval, in seconds, for collecting cache data to level-2 storage when Windows is busy. You can manually enter the value you want, and the range of setting values is 1 to 250. You can also select the following predefined values in the drop-down menu:
Note: The setting does not affect the collection behavior when Windows is idle.
Volatile Cache Contents: Cache contents in the level-2 storage are not preserved when the system is rebooted. This option is usually for multi-boot computers where another operating system may modify cached volumes, leading to the inconsistency between cache contents and source data.
Ignore Sync Check and Preserve Cache Anyway: Cache contents in the level-2 storage are not reset even if they might be out of sync with source data. This option is designed for special scenarios only. It may cause unexpected errors and corrupt target volumes. Use at your own risk!
Cache Size: The amount of the cache space. This value does not count the overhead. Generally, the larger the cache size, the better the disk performance. Of course, when you use OS managed memory as cache, you shall reserve enough memory for Windows and other applications to run and not use up all available memory. >> more
Block Size: Cache is logically partitioned into blocks of fixed size, typically ranging from 4KB to 512KB. Cache block is the smallest unit that PrimoCache manages. A smaller block size brings more available blocks for the same amount of cache space and usually higher performance. However, it will need larger memory overhead and may cause heavy CPU overload. To reach the best performance, a value equal to or less than the cluster size of the file system is recommended.
Defer-Write: If this option is checked, the Defer-Write function will be enabled, which can greatly improve the writing speed of the system and reduce the write wear of the disk. See Defer-Write for details.
Note: If all cache spaces are set to "100% Read", this option is greyed and disabled.
Latency: Specifies the time interval, in seconds, at which cache task periodically flushes deferred write-data from cache to disk. You can manually enter the value you want.
Advanced Defer-Write Options:
Write Mode: Specifies the behavior of writing deferred write-data to the underlying disk.
Free Cache on Written: If checked, cache blocks that store deferred write-data will be marked as standby blocks after the data is written to disk. When all empty blocks are used up, these blocks will be selected first to store new data. If this option is not checked, these blocks will be marked as used blocks and selected according to the normal cache replacement algorithm. >> related information
Flush on Sleep: If checked, all deferred write-data will be flushed to disk when Windows goes to sleep.
Regardless of whether this option is checked, all deferred write-data will be flushed to disk when Windows goes to hibernate.
Flush L1 to L2: This option is valid only when Defer-Write is enabled on both L1 cache and L2 cache. If this option is checked, when the L1 cache is full of deferred write-data, the data will be transferred to the L2 cache instead of being directly written to the disk.
Skip Flush on Shutdown: If checked, current deferred write-data will NOT be flushed to disk at computer shutdown. This option is designed for special scenarios only. Do NOT enable it under normal circumstances, or it may completely corrupt volumes being cached.
Prefetch Last Cache: If this option is checked, PrimoCache will automatically load the last cached data into the L1 cache after the computer restarts, thereby improving the speed of the first data read. This option has no effect on the L2 cache, because the L2 cache is persistent, and the cached data still exists after restart.
Start at Windows Boot: By default, prefetch starts after a period of idle time since you logs on to Windows. If this option is enabled, prefetch starts as early as when Windows starts up. Enabling this option may increase the Windows boot-up time.
Lock Cache Content: The cache content to be prefetched is locked to the content of last Windows run and won't be varied on next Windows runs. This option is usually enabled when you see that last Windows run has a good cache hit rate and want to keep this cache content for prefetching on next Windows runs.