WOS and ROS
Moderator: NorbertKrupa
WOS and ROS
What are the differences between the WOS and the ROS? What are they used for and if ROS is faster why use WOS? Any why do these acronyms remind me of characters from the TV show friends?
- JimKnicely
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Re: WOS and ROS
Hi,
The ROS isn't "faster" than the WOS per se, it's just more organized
The Write Optimized Store (WOS) is stored in memory (RAM) while the Read Optimized Store (ROS) is stored on your hard disk. Typically the WOS should be faster for read and write operations, but since its RAM you have a lot less of it. To further increase the performance of data loads into the WOS, Vertica stores the data in it without any type of sorting, compression or indexing. The ROS on the other hand is a highly optimized via compression and indexing. Since the ROS is so highly organized we experience the best performance from it when reading the massive amounts of table data we'd expect to retrieve from a data warehouse.
If you execute a standard INSERT, UPDATE, DELETE or COPY (without the DIRECT hint) command any affected data will be stored in the WOS. But if you execute an INSERT with the /*+ direct */ hint or a COPY (with the DIRECT hint) affected data will be stored "directly" in the ROS.
Note that a component of Vertica called the Tuple Mover (TM) migrates data from memory (WOS) to disk (ROS).
Let's run through an example of how data moves into and out of the WOS and ROS. I'll create a table named WOS_ROS_TEST for the exercise:
Next I'll add some records using standard INSERT statements:
We can query the PROJECTION_STORAGE system table to find out if the data for this table is stored in the WOS or the ROS:
The above query shows that all three records are stored in the WOS (the wos_row_count column = 3).
Now I'll add more records to the table table, but this time I'll include the DIRECT hint:
Once again, we can query the PROJECTION_STORAGE table to find out where these new records are stored:
The above query shows that the three new records were stored directly to the ROS (ros_row_count = 3)!
So how does data move from the WOS to the ROS? It's the job of the Tuple Mover process. There are several system parameters that control when the Tuple Mover does its thing but I'll leave a discussion of those for another post. In the mean time, if we don't want to wait around, we can force the Tuple Mover to move the data for a table:
Now all the records are happily stored in the ROS on disk (ros_row_count = 6).
The ROS isn't "faster" than the WOS per se, it's just more organized
The Write Optimized Store (WOS) is stored in memory (RAM) while the Read Optimized Store (ROS) is stored on your hard disk. Typically the WOS should be faster for read and write operations, but since its RAM you have a lot less of it. To further increase the performance of data loads into the WOS, Vertica stores the data in it without any type of sorting, compression or indexing. The ROS on the other hand is a highly optimized via compression and indexing. Since the ROS is so highly organized we experience the best performance from it when reading the massive amounts of table data we'd expect to retrieve from a data warehouse.
If you execute a standard INSERT, UPDATE, DELETE or COPY (without the DIRECT hint) command any affected data will be stored in the WOS. But if you execute an INSERT with the /*+ direct */ hint or a COPY (with the DIRECT hint) affected data will be stored "directly" in the ROS.
Note that a component of Vertica called the Tuple Mover (TM) migrates data from memory (WOS) to disk (ROS).
Let's run through an example of how data moves into and out of the WOS and ROS. I'll create a table named WOS_ROS_TEST for the exercise:
Code: Select all
dbadmin=> create table wos_ros_test (pk int, name varchar(100));
CREATE TABLE
Code: Select all
dbadmin=> insert into wos_ros_test values (1, 'Jim');
OUTPUT
--------
1
(1 row)
dbadmin=> insert into wos_ros_test values (2, 'Jane');
OUTPUT
--------
1
(1 row)
dbadmin=> insert into wos_ros_test values (3, 'Josh');
OUTPUT
--------
1
(1 row)
Code: Select all
dbadmin=> select node_name, wos_row_count, ros_row_count from projection_storage where anchor_table_name = 'wos_ros_test';
node_name | wos_row_count | ros_row_count
----------------------+---------------+---------------
v_intersect_node0001 | 3 | 0
v_intersect_node0002 | 3 | 0
v_intersect_node0003 | 3 | 0
(3 rows)
Now I'll add more records to the table table, but this time I'll include the DIRECT hint:
Code: Select all
dbadmin=> insert /*+ direct */ into wos_ros_test values (4, 'Peng');
OUTPUT
--------
1
(1 row)
dbadmin=> insert /*+ direct */ into wos_ros_test values (5, 'Joe');
OUTPUT
--------
1
(1 row)
dbadmin=> insert /*+ direct */ into wos_ros_test values (6, 'Pert');
OUTPUT
--------
1
(1 row)
Code: Select all
dbadmin=> select node_name, wos_row_count, ros_row_count from projection_storage where anchor_table_name = 'wos_ros_test';
node_name | wos_row_count | ros_row_count
----------------------+---------------+---------------
v_intersect_node0001 | 3 | 3
v_intersect_node0002 | 3 | 3
v_intersect_node0003 | 3 | 3
(3 rows)
So how does data move from the WOS to the ROS? It's the job of the Tuple Mover process. There are several system parameters that control when the Tuple Mover does its thing but I'll leave a discussion of those for another post. In the mean time, if we don't want to wait around, we can force the Tuple Mover to move the data for a table:
Code: Select all
dbadmin=> select do_tm_task('moveout', 'wos_ros_test');
do_tm_task
-------------------------------------------------------------------------------------
Task: moveout
(Table: public.wos_ros_test) (Projection: public.wos_ros_test_node0001)
(Table: public.wos_ros_test) (Projection: public.wos_ros_test_node0002)
(Table: public.wos_ros_test) (Projection: public.wos_ros_test_node0003)
(1 row)
dbadmin=> select node_name, wos_row_count, ros_row_count from projection_storage where anchor_table_name = 'wos_ros_test';
node_name | wos_row_count | ros_row_count
----------------------+---------------+---------------
v_intersect_node0001 | 0 | 6
v_intersect_node0002 | 0 | 6
v_intersect_node0003 | 0 | 6
(3 rows)
Jim Knicely
Note: I work for Vertica. My views, opinions, and thoughts expressed here do not represent those of my employer.
Note: I work for Vertica. My views, opinions, and thoughts expressed here do not represent those of my employer.
Re: WOS and ROS
Excellent and made easy by knicely
One more difference I would like to mention
WOS is Row store
ROS is Columnar Store
WOS is mostly used for Trickle loading
ROS is mostly used for Bulk Loading
sometimes Vertica is also refered as a Hybrid Database as it has a Row store and a Column store.
One more difference I would like to mention
WOS is Row store
ROS is Columnar Store
WOS is mostly used for Trickle loading
ROS is mostly used for Bulk Loading
sometimes Vertica is also refered as a Hybrid Database as it has a Row store and a Column store.
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- Intermediate
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Re: WOS and ROS
hi guys,
Once you made a bulk load, vertica initially stores it in WOS, where the data gets stored in unoptimised way.
But after some time , it performs MOVEOUT operation automatically.
And then , the data retrieval becomes faster. (Correct me if i am wrong).
Now , my question is after how much time , it would move the data from WOS to ROS??
And if i do tuple mover operation , does it makes my database faster (Without running the database designer)???
PLease help me..
Thanks,
Raj!!
Once you made a bulk load, vertica initially stores it in WOS, where the data gets stored in unoptimised way.
But after some time , it performs MOVEOUT operation automatically.
And then , the data retrieval becomes faster. (Correct me if i am wrong).
Now , my question is after how much time , it would move the data from WOS to ROS??
And if i do tuple mover operation , does it makes my database faster (Without running the database designer)???
PLease help me..
Thanks,
Raj!!
Rajasekhar.T|HP ATP Vertica Big Data Solutions V1
Re: WOS and ROS
Hi!
>> Once you made a bulk load, vertica initially stores it in WOS...
Not exactly, depends on what type of bulk load you choosed: AUTO/DIRECT/TRICKLE.
http://en.wikipedia.org/wiki/Bulk_insert
(for Vertica it's COPY statement only)
>> PLease help me..
Google,Wiki and Vertica Docs - your are best friends, try to find answer by yourself, don't try just to get the answer("and you will find that world much more interesting and your knowledge increased")
>> Once you made a bulk load, vertica initially stores it in WOS...
Not exactly, depends on what type of bulk load you choosed: AUTO/DIRECT/TRICKLE.
http://en.wikipedia.org/wiki/Bulk_insert
(for Vertica it's COPY statement only)
- AUTO/DIRECT/TRICKLE
https://my.vertica.com/docs/6.1.x/HTML/ ... m#1668.htm
Specifies the method COPY uses to load data into the database. The default load method is AUTO, in which COPY loads data into the WOS (Write Optimized Store) in memory. When the WOS is full, the load continues directly into ROS (Read Optimized Store) on disk. - Loading Directly into WOS (AUTO)
https://my.vertica.com/docs/6.1.x/HTML/ ... #17615.htm
This is the default load method. If you do not specify a load option, COPY uses the AUTO method to load data into WOS (Write Optimized Store in memory). The default method is good for smaller bulk loads (< 100MB). Once WOS is full, COPY continues loading directly to ROS (Read Optimized Store on disk) containers. - WOS Overflow
https://my.vertica.com/docs/6.1.x/HTML/ ... m#4983.htm
The WOS exists to allow Vertica to efficiently batch small loads into larger ones for I/O purposes. Loading to the WOS is fast because the work of sorting, encoding, and writing to disk is deferred and performed in the background by the Tuple Mover's moveout process. Since the WOS has a finite amount of available space, it can fill up and force Vertica to spill small loads directly to disk. While no data is lost or rejected when the WOS gets full, it can result in wasted I/O bandwidth. Thus, follow the Tuning the Tuple Mover guidelines to avoid WOS overflow. - Tuple Mover Configuration Parameters
https://my.vertica.com/docs/6.1.x/HTML/ ... #14361.htm
The following configuration parameters control how the Tuple Mover operates. You can use them to adjust its operation to suit your needs, as described in the following sections.- ActivePartitionCount
- MergeOutInterval
- MoveOutInterval
- MoveOutMaxAgeTime
- MoveOutSizePct
>> PLease help me..
Google,Wiki and Vertica Docs - your are best friends, try to find answer by yourself, don't try just to get the answer("and you will find that world much more interesting and your knowledge increased")
Re: WOS and ROS
Good discussion.
What is the benefit of having WOS? Why do not we load it directly into ROS? I understand that WOS is for trickle feed and ROS is for bulk load. Why can not Vertica have just ROS?
What is the benefit of having WOS? Why do not we load it directly into ROS? I understand that WOS is for trickle feed and ROS is for bulk load. Why can not Vertica have just ROS?
Re: WOS and ROS
Hi!
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Last edited by id10t on Fri May 08, 2015 4:48 pm, edited 1 time in total.