Hi Satoshi, Incremental Backup if set to True, copies SSTables to the backup folder as soon as a SSTable is flushed to disk. Hence these backed up SSTables miss out on the opportunity to go through compaction. Does that explain the longer time ?
- Rajath ------------------------ Rajath Subramanyam On Fri, Jul 15, 2016 at 12:20 AM, Satoshi Hikida <sahik...@gmail.com> wrote: > Hi Prasenjit > > Thank you for your reply. > > However, I doubt that incremental backup can reduce RTO. I think the > demerit of incremental backup is to take longer repair time rather than > without incremental backup. > > Because I've compared the repair time of two cases like below. > > (a) snapshot(10GB, full repaired) + incremental backup(1GB) > (b) snapshot(10GB, full repaired) > > Each case consists of 3 node cluster, replication factor is 3 and total > data size is 12GB/node. And we assume one node got failure then we restore > the node. The result showed that case (b) is faster than case (a). The > repair process of the token ranges included in incremental backup was very > slow. However, the just transferring replicated data from existing nodes to > repairing node is faster than repair. > > So far, I think Pros and Cons of incremental back is as following: > > - Pros (There are already agreed by you) > - It allows storing backups offsite without transferring entire snapshots > - With incremental backups and snapshots, it can provide more recent RPO > (Recovery Point Objective) > - Cons > - It takes much longer repair time rather than without incremental backup > (longer RTO) > > > Is it correct understand? I would appreciate you can give me any advice or > ideas if I was misunderstanding. > > > Regards, > Satoshi > > > On Fri, Jul 15, 2016 at 1:46 AM, Prasenjit Sarkar < > prasenjit.sar...@datos.io> wrote: > >> Hi Satoshi >> >> You are correct that incremental backups offer you the opportunity to >> reduce the amount of data you need to transfer offsite. On the recovery >> path, you need to piece together the full backup and subsequent incremental >> backups. >> >> However, where incremental backups help is with respect to the RTO due to >> the data reduction effect you mentioned. The RPO can be reduced only if you >> take more frequent incremental backups than full backups. >> >> Hope this helps, >> Prasenjit >> >> On Wed, Jul 13, 2016 at 11:54 PM, Satoshi Hikida <sahik...@gmail.com> >> wrote: >> >>> Hi, >>> >>> I want to know the actual advantage of using incremental backup. >>> >>> I've read through the DataStax document and it says the merit of using >>> incremental backup is as follows: >>> >>> - It allows storing backups offsite without transferring entire snapshots >>> - With incremental backups and snapshots, it can provide more recent RPO >>> (Recovery Point Objective) >>> >>> Is my understanding correct? I would appreciate if someone gives me some >>> advice or correct me. >>> >>> References: >>> - DataStax, "Enabling incremental backups", >>> http://docs.datastax.com/en/cassandra/2.2/cassandra/operations/opsBackupIncremental.html >>> >>> Regards, >>> Satoshi >>> >> >> >
