Hi,
I'd like to evaluate mariadb-galera on some test databases. Our load
is at least 90% writes coming from a datastream and I would try to
set
up a real-world situation and test with real data.
Most of the work load is "insert ... on duplicate key update"
mass-inserts (actually updates) of about 4MB/10000 rows each. 99% of
these run onto 3-4 tables (each around 10GB/7 million rows of size).
Total database size is around 800 GB.
We have a traditional statement-based master-slave replication, but
all these mass-inserts run over a proxy with SET SQL_LOG_BIN=0 in
parallel on all systems - no way to process this amount of data
single-threaded on the slaves. I was hoping galera would make this
easier and make our proxies obsolete.
I have some servers I could use for galera as a first step. I wanted
to do this for 4 months now but never got into it, I read your
request
to test the RC and think I should start now hoping to be able to give
some valuable feedback:
After reading through the documentation and some blogs I have some
doubts, but my idea was to do the following:
I'd clone the database of an existing slave to a new machine with
mariadb-galera (name the host "testgalera1" and rsync the database or
use mysqldump). I'd then set up this one as a "normal" statement
based
slave connected to one of our masters? Afterwards, the next host
"testgalera2" would have to be added to the galera-cluster? And after
that, I'd set up one of our older database servers and add that to
the
cluster, too. My idea was to take an older, slower system to see how
much this slowes the cluster down and get an idea how much headroom
I'd have when I leave those old machines out (the old machines have
only 64GB of RAM and slower CPUs).
I'd then modify my proxy for all the incoming inserts and add a
writer-thread to one of the hosts in the cluster, that data should be
replicated by galera to all other galera hosts. All other data should
be coming in via the "traditional" replication thread of testgalera1.
This should give me a 95-99% real world write situation on the
cluster.
Adding a host to a running cluster would mean cloning the whole
database (of course), but this also means the host I copy from would
have to block write access to its tables and buffer all modifications
in memory (at least that's how I read the documentation) during the
copy process. Looking at the database size and amount of inserts, I
am
afraid adding a host to the cluster without taking everything down
would be impossible - or even if it works fine now it could cause
trouble once the database gets just a little bit larger or my load
increases a bit.
before I start with this - is galera an insane idea regarding my
load? Or is it worth a try?
Jan
some numbers of some of the old databases:
innodb_buffer_pool_size between 60-120 GB depending on server memory
configuration.
db5: Uptime: 8052248 Threads: 44 Questions: 1413881794 Slow
queries: 160049 Opens: 683779 Flush tables: 2 Open tables: 1024
Queries per second avg: 175.588
db6: Uptime: 8070552 Threads: 6 Questions: 873413218 Slow queries:
3208 Opens: 336584 Flush tables: 1 Open tables: 578 Queries per
second avg: 108.222
db7: Uptime: 4175032 Threads: 28 Questions: 639627677 Slow
queries: 139337 Opens: 522673 Flush tables: 1 Open tables: 2016
Queries per second avg: 153.203
db7# mysql -e 'show global status like "%com\_%" ' |grep -v '\s0$'
Variable_name Value
Com_admin_commands 289127
Com_alter_table 6269
Com_analyze 725
Com_begin 3712141
Com_change_db 80112
Com_commit 3999309
Com_create_db 1
Com_create_table 253849
Com_create_trigger 10
Com_create_view 68
Com_delete 12365037
Com_delete_multi 7
Com_drop_table 310771
Com_drop_trigger 10
Com_drop_view 65
Com_empty_query 509
Com_flush 48
Com_grant 36
Com_insert 314280963
Com_insert_select 613565
Com_kill 214
Com_lock_tables 85
Com_optimize 1
Com_purge 2320
Com_rename_table 11
Com_repair 1
Com_replace 14240825
Com_replace_select 29920
Com_revoke 8
Com_rollback 13
Com_select 178540996
Com_set_option 6886915
Com_show_binlogs 69960
Com_show_charsets 1542
Com_show_collations 1544
Com_show_create_db 28
Com_show_create_func 195
Com_show_create_table 53282
Com_show_create_trigger 1
Com_show_databases 43584
Com_show_events 3
Com_show_fields 131874
Com_show_function_status 45
Com_show_grants 335
Com_show_keys 2582
Com_show_master_status 142
Com_show_plugins 7224
Com_show_procedure_status 45
Com_show_processlist 116918
Com_show_slave_status 83193
Com_show_status 155732
Com_show_storage_engines 25
Com_show_table_status 7439
Com_show_tables 1973739
Com_show_triggers 538
Com_show_variables 85034
Com_show_warnings 766
Com_stmt_close 363
Com_stmt_execute 363
Com_stmt_prepare 363
Com_truncate 452
Com_unlock_tables 79
Com_update 34496744
Com_update_multi 408212
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