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What Is Using The Most Space In Your Database ?

As I work on moving a large system with multiple database servers from a 27TB SAN to a single database server with about 6TB of direct attached storage (DAS), I have to worry much more about space utilization. The stakes are also a little higher, since it is much harder to add space with DAS than with a modern SAN.

There are several aspects to this problem, such as how large are your data files, how full are they, and how large are your database backup files. Within a database, you need to be aware of what tables and indexes are using the most space, and how much fragmentation your indexes have. Rebuilding or reorganizing an index can reclaim a lot of wasted space if the index was heavily fragmented. Looking for unused or duplicate indexes is also important.

Luckily, I am running SQL Server 2008 Enterprise Edition, so I have a few weapons to make this a little easier. These include data compression and native backup compression, which are both new Enterprise-only features in SQL Server 2008.  These allow you to save space and I/O at the cost of some CPU.

These four queries are very helpful in an effort like this. The first one shows me how large my data files and log files are, and how full they are.  The second one shows all the user table names, their row counts, and data compression status. The third query shows the row count, data and index size for each user table in the current database, while the fourth query shows recent compressed full backup results on the entire instance.

    -- Individual File Size query
    SELECT name AS [File Name] , file_id, physical_name AS [Physical Name], 
    size/128 AS [Total Size in MB],size/128.0 - CAST(FILEPROPERTY(name, 'SpaceUsed') AS int)/128.0 
    AS [Available Space In MB]
    FROM sys.database_files;
    -- Get Table names, row counts, and compression status (SQL 2008 Only)
    SELECT OBJECT_NAME(object_id) AS [Table Name], SUM(Rows) AS [Row Count], 
           data_compression_desc AS [Compression]
    FROM sys.partitions 
    WHERE index_id < 2 --ignore the partitions from the non-clustered index if any
    AND OBJECT_NAME(object_id) NOT LIKE 'sys%'
    AND OBJECT_NAME(object_id) NOT LIKE 'queue_%' 
    AND OBJECT_NAME(object_id) NOT LIKE 'filestream_tombstone%' 
    GROUP BY object_id, data_compression_desc
    -- Get count of rows, data and index size in current database
    SELECT  object_name(id) AS [TableName], rowcnt AS [Rows], 
           (dpages * 8)/1024 AS [DataSize_MB], 
           ((SUM(used) * 8) - (dpages * 8))/1024 AS [IndexSize_MB]
    FROM sys.sysindexes 
    WHERE indid IN (0,1) 
    AND OBJECTPROPERTY(id, 'IsUserTable') = 1 
    GROUP BY id, rowcnt, reserved, dpages
    ORDER BY dpages DESC; 
    -- Look at recent compressed full backups (SQL 2008 Only)
    SELECT TOP (5) bs.server_name, bs.database_name AS [Database Name], 
    CONVERT (BIGINT, bs.backup_size / 1048576 ) AS [Uncompressed Backup Size (MB)],
    CONVERT (BIGINT, bs.compressed_backup_size / 1048576 ) AS [Compressed Backup Size (MB)],
    CONVERT (NUMERIC (20,2), (CONVERT (FLOAT, bs.backup_size) /
    CONVERT (FLOAT, bs.compressed_backup_size))) AS [Compression Ratio], 
    DATEDIFF (SECOND, bs.backup_start_date, bs.backup_finish_date) AS [Backup Elapsed Time (sec)],
    bs.backup_finish_date AS [Backup Finish Date]
    FROM msdb.dbo.backupset AS bs 
    WHERE DATEDIFF (SECOND, bs.backup_start_date, bs.backup_finish_date) > 0 
    AND bs.backup_size > 0
    AND bs.type = 'D' -- Change to L if you want Log backups
    ORDER BY bs.backup_finish_date DESC;


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