Storage Configuration
Storage is a critical factor of any database system. All activities being performed by users is being stored ultimately on data storage devices. Storage disk array is a single point of failure which can bring down an entire cluster setup. To address the data availability, the data and logs should be placed on a fault tolerant external storage arrays which supports high volume of disk I/O with high speed performance. RAID storage arrays are most popular solutions in storage world; let’s take a look at the RAID options available.
RAID Configurations Overview – Redundant Array of Independent Disks
RAID provides a method of accessing multiple individual disks as if the array were one larger disk, spreading data access out over multiple disks, thereby reducing the risk of losing all data if one drive fails, and improving access time.
Data Placement
For optimum disk I/O performance, data and log devices, including tempdb, should be placed on separate disk arrays. In a large OLAP system the database resources are used differently than OLTP systems. If an OLAP system uses tempdb heavily, then moving it into a different drive, which contains multiple fast disks, would boost the I/O performance.
-
Data files – Data drives should use the RAID configuration of 0+1, also known as Disk-Striping + Disk-Mirroring; or 1+0, also known as Disk-Mirroring + Disk-Striping. 0+1 means that first the drives are striped as one set and then mirrored. 1+0 means that first drives are mirrored and then whole thing is striped. RAID level 0+1 give a little better performance while comparing to 1+0. RAID level 1+0 is proven to be better in terms of fault tolerance when compared to 0+1.
-
Log files – Log drives can be configured either with RAID 1, which is plain mirroring, or striped mirrors/mirrored stripes. Logs are important to protect, so choose the appropriate availability of the disk for your high availability plan.
-
Tempdb files – Microsoft recommends placing the tempdb on a fast I/O subsystem to get good performance. In this case, use RAID 0+1 disks for tempdb database.
Disk Configuration Dynamic / Basic
Dynamic Disk configuration is not supported in Windows Clustering. A disk initialized for dynamic storage is called a dynamic disk. It can hold simple volumes, spanned volumes, mirrored volumes, striped volumes, and RAID-5 volumes. With dynamic storage, you can perform disk and volume management without having to restart the operating system.
Basic Disk configuration uses normal partition tables supported by all versions of Windows, MS-DOS, and Windows NT. A disk initialized for basic storage is called a basic disk. It can hold primary partitions, extended partitions, and logical drives. Basic volumes include partitions and logical drives, as well as volumes created using Windows NT 4.0 or earlier, such as volume sets, stripe sets, mirror sets, and stripe sets with parity. In Windows 2000, these volumes are called spanned volumes, striped volumes, mirrored volumes, and RAID-5 volumes, respectively.
File Compression
File compression is not supported on a clustered database server.
Software RAID
Software RAID is not supported in a clustering environment. Hardware level RAID must be used.
SAN Disks Layout for 4 Node 4 Instance Active / Active Setup
Other Considerations
MS Exchange
It is not recommended to have both SQL Server 2000 and Microsoft Exchange 2000 on the same cluster