Space Saved With Exadata Hybrid Columnar Compression
Posted by Tyler Muth on June 8, 2010
I’ve been working with Exadata lately so I thought I’d share some numbers on HCC and Advanced Compression using ALL_OBJECTS. This is a virtualized environment so I don’t have any real performance numbers to post, but the compression ratio is still impressive. Most people think of compression in terms of saving space, but it also has a performance benefit for large table scans since it reduces physical IO.
create table all_objs as select a.* from all_objects a; create table all_objs_compressed_oltp compress for all operations as select a.* from all_objects a; create table all_objs_compressed_query compress for query as select a.* from all_objects a; create table all_objs_compressed_archive compress for archive as select a.* from all_objects a; select segment_name,round(bytes/1024/1024,3) size_mb from user_segments where segment_name like 'ALL_OBJS%' order by 2 desc nulls last; SEGMENT_NAME SIZE_MB ---------------------------- ---------------------- ALL_OBJS 7 ALL_OBJS_COMPRESSED_OLTP 2 ALL_OBJS_COMPRESSED_QUERY 0.375 ALL_OBJS_COMPRESSED_ARCHIVE 0.375
So, for Advanced / OLTP Compression (compress for all operations) we achieve a compression factor of 3.5x. For HCC our compression factor jumps to 18.7x! Extrapolating a bit, a 1 TB table becomes a 55 GB table! Not sure why the compression ratio for Query and Archive is the same…
Physical I/O Saved With Exadata Hybrid Columnar Compression « Tyler Muth’s Blog said
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