Disk Configuration with Ingres

Transcription

1 Disk Configuration with Ingres September 2008

2 About the Presenter Chip Nickolett has been using Ingres since 1986, and became a DBA in 1989 He has configured many high-performance, highavailability production systems He has performed many customer and vendor benchmarks using Ingres He is currently the Director of Consulting Services in the Americas and can be reached via at chip.nickolett@ingres.com

3 Agenda Why Focus on Disk? Goals of Disk Configuration Data Integrity Performance Ease of Management Types of Disk RAID Partitioning Planning Based on Need and/or Capacity Summary Q&A

4 Why Focus on Disk? Slowest sub-system in any computer Orders of magnitude slower than other forms of data transfer Disks are getting bigger, but not necessarily faster It s easier than ever to create problems! Basic disk geometry is the same, and larger disk drives just aggravate performance issues Has the potential to improve performance and enhance the maintainability of your system!

5 Why Focus on Disk? (cont.)

6 Goals of Disk Configuration 1. Data Integrity First and foremost, the Ingres system needs to be configured in a way that will prevent data loss This is the first step of a comprehensive integrity plan that includes journaling & checkpointing 2. Performance Routine operations / use Daily Management / Periodic Maintenance 3. Ease of ongoing management Capacity Planning

7 Data Integrity It is important to separate key areas of Ingres for maximum recoverability Data Checkpoints, Journal, and Dump Files Transaction Log Could be combined with the checkpoint / journal / dump files if needed, but there could be performance issues by doing this due to high I/O loads Having all Ingres locations on a single disk drive is very risky since you could lose everything! (SPOF)

8 Performance Consistency over Peak Performance is most desirable for most production systems People will accept 1-second screen-to-screen or query execution performance People will become frustrated if 90% of all performance is sub-second, but the remaining 10% is 2-3 seconds Balanced I/O loads help provide that consistency Sharing disks with other systems can negatively impact consistency

9 Performance (cont.) Multi-location tables using multiple physical locations can greatly improve performance since Ingres knows exactly which location to search This is because data pages are written in a roundrobin manner, and using the TID (tuple identifier) Ingres can determine the page. Since Ingres knows how many locations there are it can mathematically calculate the exact location to search Table Partitions can improve performance by segregating data in a meaningful way to reduce I/O

10 Performance (cont.) Mapping the disk block size to Ingres page sizes and group read sizes (e.g., eight 2K pages, or 16K reads is the default 2K configuration) can minimize physical I/O requests Goal is to ensure that an Ingres I/O request does not take more than one physical I/O request Having a larger disk block size (such as 128K) is better than having a smaller block size (such as 1K) This is not much of an issue with modern hardware since default block sizes are typically large

11 Ease of Management Consistency is also good for physical schemas My preference is to stripe (i.e., use multi-location tables) all tables and all indexes against all defined Ingres locations Configure all tables in one direction (location 1 through location 5), and all indexes in the opposite direction (location 5 through location 1). This balances disk utilization as well as I/O. This makes the installation easy to manage and minimizes problems with locations filling-up

12 Ease of Management (cont.)

13 Types of Disk SAN, NAS, Direct Attached Storage, Local Disk Which is Best? NAS is typically the worst performer SCSI, SAS, SATA? SAS tends to be the fastest SATA tends to be cheaper per GB Don t see much pure SCSI anymore Large versus small, 10K RPM versus 15K RPM Faster is always better Smaller drives tend to have less I/O contention

14 Types of Disk (cont.) Hardware specification best practices: Specify as much cache on the controller as you can. Having 32 GB+ is not uncommon on large systems Specify as much on-board disk cache as you can (8 MB should be a minimum) Specify the fastest interconnect you can afford Fibre is always a good choice Specify the greatest number of spindles (physical disks) you can accommodate and/or afford Specify the fastest disk you can afford (15K RPM)

15 RAID RAID 0 (striping) is OK but unnecessary RAID 1 (mirroring) is ideal RAID 5 is common but not ideal from an I/O write performance perspective Can be masked by controllers with large cache Once the controller becomes saturated there is usually significant performance degradation RAID 6 (striped with dual-parity) becoming more popular on high-end equipment

16 Partitioning Good way to segregate data to minimize target areas (e.g., sales information partitioned by year) Can reduce the volume of data Ingres needs to use Can be beneficial with parallel queries May require additional maintenance (e.g., creating a new partition every year, as in the example above) This is a great way to manage large volumes of data (.75 TB or larger)

17 Planning based on Need and/or Capacity It is always easier and better to plan for what you anticipate needing over the course of the next 2-3 years, than continually expanding your environment Problems often occur when locations are added on the fly and then only a few tables relocated to those locations Ad hoc expansion could impact parallel checkpoints and recovery! Use consistent naming conventions Benchmark under load to ensure that the underlying architecture meets your requirements

18 Summary It is always better to design a system for performance than to try to back it in later Configuration and Capacity Planning are important Ingres provides many ways to manage large volumes of data in ways that are easy to manage and provide very high-performance The tips provided can benefit any size installation There is a complementary white paper titled, Disk Configuration Tips for High-Performance Installations available on the Ingres.com site

19 Questions? 2008 Ingres Corporation Slide