Is there a lot disparity between flash caching software products available today? For example, how does flash caching software from companies like Velobit and Nevex compare to flash cache products from major storage vendors like EMC and NetApp?
Yes, there are huge differences. The majority of caching software is block-based (such as Velobit), meaning it is used with SAN storage. It caches blocks based on an algorithm. That algorithm can be based on frequency of access where it puts the data into the cache when it meets certain frequency levels and takes it out when those levels drop.
Some algorithms are based on data age. New data is always placed in the cache. As it ages, it's purged. Some caching software even allows specific data to be "pinned" in the cache so that it is always there. The only file-level caching software is Nevex (recently acquired by Intel).
This was first published in January 2013