1. Reads mostly go to the primary but yes, in some circumstances it’ll read from the backup with that configuration set to true
2. No. It’ll “rebalance,” which means backup partitions would be promoted to primaries. Your client would still get a response 3. Yes — though in practice the window is very small. Use FULL_SYNC and/or readFromBackup=false if you need to avoid that 4. You’d get one copy per node. Think of it as a target rather than a guarantee > On 3 Nov 2020, at 02:50, Mahesh Renduchintala > <mahesh.renduchint...@aline-consulting.com> wrote: > > Hi > > I have a large SQL table (12 million records) in cacheMode partitioned. > This table is distributed over two server nodes > > > -1- > > When running a large SELECT from a thick client node, could data be fetched > from the backup instead of primary partitions? > Below is the configuration. > > <property name="cacheMode" value="PARTITIONED"/> > <property name="backups" value="2"/> > <property name="atomicityMode" value="TRANSACTIONAL"/> > <property name="writeSynchronizationMode" value="PRIMARY_SYNC"/> > <property name="rebalanceMode" value="ASYNC"/> > <property name="statisticsEnabled" value="true"/> > <property name="readFromBackup" value="true"/> > <property name="queryParallelism" value="2"/> > /> > > We are seeing some performance improvement, since we made regardFromBackup= > False and a few other things. > > -2- > in a two server system, if readFromBackup = False for a cache, and if one > server fails, > > would 2nd server stop serving client requests since some partition data is in > the backup? > > > -3- > is it possible that readFromBackup=True and Primary_Sync mode for a cache > could give inconsistent data for cacheMode Replicated in a 2 server node? > > > -4- > if I increase backup= 10, in a 2 server system, would it mean that there are > 10 backups. > > I am guessing, ignite would keep a single back up on each server, not 5 and 5 > on each server. > a new backup is created for that cache for any new node joining the cluster. > is this right understanding? > > > > > Strong > > regards > mahesh
