I have vague memories (excuse the pun) that it is better to use memory variables rather than access data from files because of hard-drive relatively slow access times?
Please note the title should be SSD and not SDD the three letter acronym for Solid State Drives.
Mods please feel free to modify this post.
SSDs are not as fast as memory. They probably never will be due to bus speeds, something else would need to change before we could get non-volatile storage as fast as RAM.
SSDs also suffer from degradation from being written to too much, you should always remove page file or reduce swap drive and enable trim when using a SSD which forces your computer to not use ROM memory for volatile storage.
Most SSD’s are in the 300-900mb/s read/write speeds. DDR3 ram is about 20,000mb/s. Access times are much faster as well. SSDs are measured in Microseconds, where RAM is measured in nanoseconds (1 micro = 1000 nano).
So, there is a bigger speed difference between RAM and SSDs than there is between SSDs and HDDs.
Spot on mawburn.
A real world application that shows this is memcached. You store your data in RAM, as opposed to a database or file caching, for the very reasons mentioned above.
That or Redis. I’ve never dealt with Memcached and only recently started messing with Redis, but I’ve read multiple times about how Redis is better in pretty much every area. I don’t remember any specifics because they both kinda do the same thing: In-Memory database that has disk persistence, which also to serve as a cache for clustered systems.
Discourse uses Redis heavily, I believe.
I am amazed at the speed difference between the RAM and SSD memory.
I will endeavoure to take this into consideration when loading numerous files and see if the process can be more efficient.
Yep, definitely store appropriate data in RAM.
Where SSD’s are really beneficial is when they are used for the database. You can’t (or rather, don’t) want to store everything in memory of course, and databases are pigs with the file operations. For example, I in phpMyAdmin on my local servers, I am constantly importing sql files.
One file in particular is 32 MB. On the server running on a Western Digital Caviar Black hard drive, that file takes approximately 90 seconds to import. On the servers installed on the Samsung Evo SSD, that same file only takes about 25 seconds to import.
That is correct, and that is actually how it achieves a lot of its performance. Because it caches a lot of information in Redis making its retrieval of said information almost instantaneous.