It means that ES works well with SSDs since Lucene is write-once under the hood, so it is "easy" on the SSDs, vs other approaches which do random writes to different places causing the higher write amplification.
But, this is balanced with the fact that Lucene must also periodically merge the segments, which is in fact its own higher level form of write amplification: when you first index a doc, it's written into a new segment, but over that doc's lifetime in the index it may be copied another 4-5 times or something before it lives in a "max sized" segment. Still, that higher write amplification likely works out to much less stress on the SSD than databases that do random writes to their stores. Mike McCandless http://blog.mikemccandless.com On Tue, Dec 16, 2014 at 4:11 AM, AndrewK <[email protected]> wrote: > At the core training I attended last year there was a side note on SSD and > write amplification: roughly along the lines of: write amplification can be > a big problem with SSD (as writes can be around 4KB but deletes are often > in blocks of around 512KB, and that the problem gets worse the smaller and > the more random the writes are), but that write amplification is never an > issue in ES as all writes are sequential anyway (reading from my notes > here). > > What does that mean exactly? That write amplification *can* be a big > problem with SSD, but not with ES on SSD, or that the problem is relevant > with lots of random writes? (I suspect the former, but am not quite sure). > > -- > 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/67ed8b75-fe8b-4f40-b41a-b66cf6eb82bc%40googlegroups.com > <https://groups.google.com/d/msgid/elasticsearch/67ed8b75-fe8b-4f40-b41a-b66cf6eb82bc%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/CAD7smRc9im3H%3DfKx5hauVVZL%3DE00aUnWf-DrZtO7etPC-VzWEQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
