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replication - Approximate bytes to copy

Hi,
I have a process that replicates data periodically from one standalone (1 node) server to other. In theory it should start every 15 min.
There are 6 tables to be replicated. their size being 150 GB.
Between 2 replication there aren't many changes. I would appreciate, less than 1 GB.
My problem is that vbr approximates and replicates 35 GB.

Does someone know what files are copied ?
How to decrease these 'replication size' ? Maybe, increasing the number of ROS/files associated to these tables ?

I though of summing size of all files changed after the last replication:

select schema_name,projection_name ,sum(used_bytes)/1024/1024/1024 storage_gb
from v_monitor.storage_containers c, remote_replication_status r
where storage_type='ROS'
and
( (schema_name='s1' and projection_name like 't1_super')
or (schema_name='s2' and projection_name like 't2_super')
)
and c.end_epoch > r.replicated_epoch
group by schema_name, projection_name;

As I said, this sum is 0,1 Gb.
So, why vertica server copies 35 GB ?

Thank you,
Veronica

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Comments

  • skeswaniskeswani Employee
    edited August 2

    Its possible you are loading into inactive partitions and the TM is merging files.
    Backup occurs at a file level and if the checksum of the files does not match, rsync has to copy them over anyways to ensure a consistent snapshot.

    I can share some queries i wrote a while ago to find out what files are getting moved and how much space is needed.

    you may not be able to use them as-is, buts its a good starting point

  • skeswaniskeswani Employee

    Create a schema

    -- actual disk usage
    create table files (sz int, file varchar(200), path varchar(2000), dt timestamp, storage_id varchar(200) default substr(file,0,49) ) order by storage_id segmented by hash (storage_id ) all nodes ksafe;

    -- snapshot_info
    create table snapshot_info ( manifest_file varchar(200), storage_id varchar(200), type varchar(50) , storage_location_id int, length int, digest varchar(50)) order by storage_id segmented by hash(storage_id) all nodes ksafe;

    -- backup_info
    create table backup_info ( manifest_file varchar(200), storage_id varchar(200), type varchar(50) , ref_count int, length int, digest varchar(50)) order by storage_id segmented by hash(storage_id) all nodes ksafe;

    Load some backup file metadata into the tables

    find /location -maxdepth 10 -printf "%s|%f|%p|%TY-%Tm-%Td %TT\n" | vsql -c "copy files (sz,file, path,dt) from stdin abort on error;"

    for file in $(find /location -name *.manifest); do cat $file | sed -ne "/[objects]/,$ p;" | grep -v "[objects]" | sed 's/, /|/g' | sed "s/^/${file//\//_}|/g" ; done | vsql -c "copy snapshot_info from stdin abort on error;"

    for file in $(find /location -name backup_manifest); do cat $file | sed -ne "/[Objects]/,$ p;" | grep -v "[Objects]" | sed 's/, /|/g' | sed "s/^/${file//\//_}|/g" ; done | vsql -c "copy backup_info from stdin abort on error;";

    Generic space usage

    -- space for backup
    skeswani=> select sum(length)//10^12 TB from backup_info ;

    TB

    28
    (1 row)

    -- space on disk (mostly accurate, exclused some dfs dirs)
    skeswani=> select sum(sz)//10^12 TB from files where substr( path, position (files.storage_id in path), length(path)) = file;

    TB

    28
    (1 row)

    space common to all snapshots

    -- space common to all snapshots
    skeswani=> select sum(length)//10^12 common_size_TB from backup_info where >ref_count > 1;

    common_size_TB

    19
    (1 row)
    -- space sitting in only one snapshot.
    skeswani=> select sum(length)//10^12 common_size_TB from backup_info where >ref_count = 1;

    common_size_TB

    9
    (1 row)

  • Thank you , skeswani !
    I will check all stmt-s.
    Veronica

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