TIP TOP - OTR/EM TYRE REPAIR SPECIALIST
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TIP TOP - OTR/EM TYRE REPAIR SPECIALIST

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TIP TOP p o w e r f o r m o t i o n OTR/EM TYRE REPAIR SPECIALIST
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UK UNIX User Group – Databases and the Web
Tuning Tips for
Linux & AIX v
to run a Database
Nigel Griffiths
Linux on Power & Virtualisation
Technical Leader, IBM Europe
© 2007 IBM Corporation & UKUUGUK UNIX User Group – Databases and the Web
Abstract:
► Sitting behind any reasonable size website is some sort of
database to hold the data involved.
► This can be used to control the web output, user records or
profiles or regular database contents which are made
available or manipulated via web applications.
► It is key then for the database to perform well in its support of
the user experience.
► This session looks at the common causes of database
performance problems with the aim to make sure you don't fall
into these common traps.
► This is practical advice from the presenter's wide experience
of Linux and UNIX support and tuning, and not database
vendor specific.“
2 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Agenda
1.Scene setting and Assumptions
2.Configuration and Change control
3.Use the latest OS version
4.Burn in the box
5.Spotting single-threadedness
6.Balanced Systems
7.Waiting is not a problem
8.Disks * four …
9.Memory – Use it or lose it!
10.The problem with paging
11.Understand your virtualisation tools & effects
12.Classic bad thinking
13.Know Your tools and nmon (blatant advert)
3 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Assumptions
Database is on a server (not a PC)
 Multiple CPUs,
 Many GB of RAM,
 Many 100’s GB of disks and
 Many Processes / Users
 You have many machines to look after  Datacentre
I am biased toward what I know and have used
► I work for IBM (15 years plus 10 before that)
► Big UNIX systems: RS6000 / pSeries / System p / …
► AIX & Linux on POWER then Linux on x86 – Benchmarking + Sizing
► RDBMS Oracle, then some DB2, MySQL, Sybase, Informix
► I will try to keep the IBM content to a minimum – but it is hard for me to do 
4 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Scene Setting
Movie
5 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Scene Setting
From my personal experience (your mileage may vary)
 Performance problems reported to IBM
► 50% poor disk layout + mgmt  some disks 90%+ busy, while 50% not used at all
► 10% poor setup of RDBMS tuning parameters relating to memory use
► 10% single threaded batch applications
► 10% poorly written customer extensions to standard applications
► 5% system running with errors in the [errpt] log file (including CPU failures!!)
► 5% paging on large RAM (>2 GB) systems [vmtune not use to set min/maxperm]
► 5% OS problems already discovered and fixed but OS was not up to date
► 4% badly ported App = not compiled with optimization or on old OS version
► 1% genuine bugs in OS, RDBMS or commands
 every single one of these was reported as a problem with the hardware!!!
6 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
What is “Quality”?
CPU
► good 70%
► bad 85%
► ugly 90%+ (except batch)
Disk
► good <30%
► bad <40%
► ugly <50%+
Network 
Memory
► good <30% bandwidth
► good zero paging
► Hubs bad >70%
► bad 10 pages per second per CPU
► Switched bad is MB/s near Mb /10
► ugly any more paging+
Run Queue
► good < 2 * CPU's
7 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Configuration and Change Control
Script to document the whole config Do you know when the machine. OS,  
App, RDBMS was last changed?
1. CPU – number, type and speed
► By whom and why?
2. Memory – size
► Exactly what they did?
3. Adapters – number & type
4. Network - number & type
Save config & performance data Before5. Disks – number & type 
6. Disk layout & file systems layout Make the change
7. OS version & tuning optionsAfter
8. RDBMS versions & tuning options Makes problem determination 
10 times easier and faster9. App (s) version & tuning options
Off machine – you need this anyway for 
disaster recover – right!
8 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Use the latest OS version
Linux 
► For advanced kernel features use 2.6 kernel and the latest rev
► 100’s of man hour gone into the OS performance tuning
● why not take it for free?
► In 2.6.16 alone:
● gcc, glibc, libhugetlbfs, 64KB pages = scaling (SLES10, RHEL5)
► No excuse for the 2.4 kernel now
AIX6
► Major improvements and Power6 support at 4.7GHz CPU
► Mobility to move a CPU partition between machines while live
► Workload Partitions, JFS2 encryption & snapshots, RBAC
9 © 2007 IBM Corporation & UKUUGTuning Tips - DatabasesUK UNIX User Group – Databases and the Web
Burn in the box
Burn in – first used in mainframe
► Larger the machine the more parts and larger every year
 Hardware failures happen
► Most failures are in the first two weeks
► Then fairly random
► Some occasions after 1  2 years in small batches
 Therefore smart to burn in test for 24 hours  Before you add your data
► CPUs – just run something on each of them
► Memory – get it hot
► Disks – get them all spinning
► Adapters – get them all busy
 After this Disk protection & HA will then catch the remaining failures
10 © 2007 IBM Corporation & UKUUGTuning Tips - Databases