Cluster. The overhead is per cluster. There are two places you'll run into scaling pain here.
1) Size of the schema (which we have to serialize to send around) - too many tables, or too many columns in tables, can cause serializing schema to get really expensive and cause problems 2) Too many memtables - assume that all of them will have some tiny trivial amount of data in them, maybe 1MB. 200 * 1MB = 200MB of heap just for empty memtables. If you have a thousand tables, that's a gigabyte of heap, just for EMPTY memtables. On Fri, May 4, 2018 at 11:17 AM, Abdul Patel <abd786...@gmail.com> wrote: > I have 3 projects in pipeline adding 3 different cluster across all > environwments would too costly option :) > > So 200 tables per keyspace or per cluster? > > > On Friday, May 4, 2018, Durity, Sean R <sean_r_dur...@homedepot.com> > wrote: > >> The issue is more with the number of tables, not the number of keyspaces. >> Because each table has a memTable, there is a practical limit to the number >> of memtables that a node can hold in its memory. (And scaling out doesn’t >> help, because every node still has a memTable for every table.) The >> practical table limit I have heard is in the low hundreds – maybe 200 as a >> rough estimate. >> >> >> >> In general, we create a new cluster (instead of a new keyspace) for each >> application. >> >> >> >> >> >> Sean Durity >> >> *From:* Abdul Patel <abd786...@gmail.com> >> *Sent:* Thursday, May 03, 2018 5:56 PM >> *To:* User@cassandra.apache.org >> *Subject:* [EXTERNAL] Cassandra limitations >> >> >> >> Hi , >> >> >> >> In my environment, we are coming up with 3 to 4 new projects , hence new >> keyspaces will be coming into picture. >> >> Do we have any limitations or performance issues when we hit to a number >> of keyspaces or number of nodes vs keyspaces? >> >> Also connections limitations if any? >> >> >> >> I know as data grows we can add more nodes and memory but nor sure about >> somethinh else which need to take into consideration. >> >> >> >> >> >> ------------------------------ >> >> The information in this Internet Email is confidential and may be legally >> privileged. It is intended solely for the addressee. Access to this Email >> by anyone else is unauthorized. If you are not the intended recipient, any >> disclosure, copying, distribution or any action taken or omitted to be >> taken in reliance on it, is prohibited and may be unlawful. When addressed >> to our clients any opinions or advice contained in this Email are subject >> to the terms and conditions expressed in any applicable governing The Home >> Depot terms of business or client engagement letter. The Home Depot >> disclaims all responsibility and liability for the accuracy and content of >> this attachment and for any damages or losses arising from any >> inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other >> items of a destructive nature, which may be contained in this attachment >> and shall not be liable for direct, indirect, consequential or special >> damages in connection with this e-mail message or its attachment. >> >