Couchbase sizing notes

couchbase-sizing.txt

couchbase sizing/capacity planing

refs:

http://blog.couchbase.com/how-many-nodes-part-1-introduction-sizing-couchbase-server-20-cluster

5 key factors:

RAM
Disk
CPU
Network
Data distribution / safety


ROT minimums

3 nodes
4GB+ RAM
4+ CPU Cores
fast local storage

RAID10 - single DISK not great use LVM/RAID

Separate devices for install, data and indexes

keep working set below high water mark 
monitor cache miss ratio/ resident item ratio

compaction - tuning .....30% default threshold, 60% better fro heavy writes

cbbackup/cbrestore

per bucket, multiple buckets aggregate

RAM sizing 

Total RAM :

managed doc cache - workingset + metadata + replicas
index caching (I/O buffer) 

working set ratio : 

example ratios ..

late stage social game 0.1
biz app 0.33
ad network 1.0


Disk Sizing:

o Sustained write rate
o rebalance capacity
o compaction ~3x overhead : data and index is append only
o Total Dataset : (active + replicas + indexes)
o Append only

CPU 
o needed for XDCR, replication, compaction 
o so now 8 core instead of 4 core say
o RAM r/w perf not impacted
o min prod req : 4 cores        (8 cores for CB 4.0)
	+1 per bucket 
	+1 core per Design Doc 
	+ 1 core per XDRC stream

network - rarely important but needs to be low lat/hi tp - eliminate router hops

running in VMs

1 couchbase VM per physical host
don't overcommit

Couchbase 4.0 - MDS 

option 1. All 4 service on all nodes (aggregate sizing for Data + Index +Query)
option 2. separate services so nodes sized for workload type:
data: more node with more RAM, less disk, less CPU
index: fewer nodes with more RAM, more disk, less CPU
query: fewer modes with less RAM, less disk, more CPU


Monitoring:

o working set doesnt  fit in RAM - cache miss rate/ disk fetches
o Disk I/O not keeping up - disk write queue size
o Internal repl lag - TAP q's
o Indexing not keeping up
o XDCR lag

Query perf - increase residual RAM, used for OS buffer cache