RAM is cheap and the best method to achieve highest performance in ES. You can try search benchmarks on ES clusters with > 8 GB RAM and > 4 GB heap plus mlockall. Either with SSD or HDD you will see only tiny difference in response times after warmup. If you are only after search performance, the cost for replacing HDD with SSD is so high and the performance gain at search side is so small that it is not worth the effort.
If the index grows and exceeds the cluster capacity, you should add RAM or add nodes to grow the capacity. If you do not, a cluster will get more and more sluggish and GC overhead increases. SSD does not change that. The situation when you want constant search response times while you have growing data in your index does not depend on a question about using SSD or HDD. In ES, SSD is best for low latency for index store write access and high data throughput while bulk indexing or for retrieving large result sets with scan/scroll. If you are after this, SSD is a must. Jörg On Fri, Oct 10, 2014 at 9:23 PM, Kevin Burton <[email protected]> wrote: > > On Friday, October 10, 2014 8:39:43 AM UTC-7, Jörg Prante wrote: >> >> RAM is 1000x faster than SSD. >> > > I mean this is the big caveat isn't it? > > If you can fit your whole index in RAM, then great, go for it... but > others have loads that can't it all in RAM at which point SSD becomes a > decent option. > > Honestly for many workloads running it ALL out or SSD is an option. > > This was what I was getting at... > > To me, RAM based search isn't that interesting any more as even on fully > random IO you can saturate a gigabit link on modern SSDs... but if you're > doing crazy queries perhaps RAM is still required. > > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elasticsearch/46ba386f-0442-4a86-9c0d-bdd9f2fd8af3%40googlegroups.com > <https://groups.google.com/d/msgid/elasticsearch/46ba386f-0442-4a86-9c0d-bdd9f2fd8af3%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/elasticsearch/CAKdsXoGjQusyMezzvo5e4GYeQ33dJkPyWsZHNusrn2oWjXxX7g%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
