Presentation done by SQL Port event.

1. @murilocmiranda
http://www.sql.pt/
murilo.miranda@gmail.com

2. AGENDA

3. 1.
2.
3.
4.
5.
6.
What is a VLDB?
Typical Troubles
OS Config
Instance Config
DB Config
Maintenance
AGENDA

4. VLDB??

5. There’s no official definition.
VLDB??

6. There’s no official definition.
Typically occupying TB range.
VLDB??

7. There’s no official definition.
Typically occupying TB range.
Billions of rows.
VLDB??

8. There’s no official definition.
Typically occupying TB range.
Billions of rows.
Typically: OLAP or OLTP with
large amount of users.
VLDB??

9. Wikipedia…
A very large database, or VLDB, is a database that contains an
extremely high number of tuples (database rows), or occupies
an extremely large physical filesystem storage space. The
most common definition of VLDB is a database that occupies
more than 1 terabyte or contains several billion rows,
although naturally this definition changes over time.
VLDB??

10. SQL VS. VLDB

11. Maximum database size
SQL VS. VLDB

12. Maximum database size
524,272 TB
SQL VS. VLDB

13. Maximum data file size
Maximum log file size
16 TB
2 TB
A limit of 32.767 files which can be distributed between 32.767 filegroups.
SQL VS. VLDB

14. TYPICAL TROUBLES

15. Maintenance
TYPICAL TROUBLES

16. Backups
Maintenance
TYPICAL TROUBLES

17. Backups
Maintenance
Indexes
TYPICAL TROUBLES

18. Backups
Maintenance
Indexes
Statistics
TYPICAL TROUBLES

19. Backups
Maintenance
Indexes
Statistics
Disaster
Recovery
TYPICAL TROUBLES

20. Backups
Maintenance
Indexes
Performanc
e
Statistics
Disaster
Recovery
TYPICAL TROUBLES

21. OS CONFIG

22. Perform Volume
Maintenance
OS CONFIG

23. Turning on Instant Initialization to
speed up data file growth
and restores.
OS CONFIG

24. Storage
Layout
OS CONFIG

25. Plan an efficient storage layout.
OS CONFIG

26. Plan an efficient storage layout.
Normally, the more spread, the more
effective.
OS CONFIG

27. Plan an efficient storage layout.
Normally, the more spread, the more
effective.
Suggestion
:
SQL BIN SQL DATA SQL IDX SQL LOGS SQL TMP
OS CONFIG

28. Mountpoint
s
OS CONFIG

29. Mountpoints could be a good strategy.
OS CONFIG

30. Mountpoints could be a good strategy.
Mountpoints are persistent
directories that point to disk
volumes.
OS CONFIG

31. Pros:
•
•
•
•
Scalable.
Save drive letters (limited to 26).
Easy to add.
No need to restart SQL Server.
OS CONFIG

32. Cons:
• Looks like a simple folder.
• Need a different approach to monitor.
OS CONFIG

33. So, if you don’t know the server….
OS CONFIG

34. Partition
Alignment
OS CONFIG

35. Setting the partition offset properly can
improve up to 30% the performance.
OS CONFIG

36. Setting the partition offset properly can
improve up to 30% the performance.
Partition alignment increases throughput
(bytes/sec) and reduce disk queues.
OS CONFIG

37. Setting the partition offset properly can
improve up to 30% the performance.
Partition alignment increases throughput
(bytes/sec) and reduce disk queues.
A partition that is track misaligned will occasionally
cause 2 I/O operations instead of one.
OS CONFIG

38. Unless performed at the time of partition
creation, the default alignment offset (31,5
Kb) will result in unaligned partitions on
versions of Windows up to and including
Windows Server 2003.
OS CONFIG

39. This offset is associated with hidden sectors,
which basically store partition information.
OS CONFIG

40. This offset is associated with hidden sectors,
which basically store partition information.
Considering that:
- Each disk sector has 512 bytes.
- Win. 2003 has 63 hidden sectors.
OS CONFIG

41. This offset is associated with hidden sectors,
which basically store partition information.
Considering that:
- Each disk sector has 512 bytes.
- Win. 2003 has 63 hidden sectors.
512 * 63 = 31,5 Kb
OS CONFIG

42. Example:
Stripe Unit Size:
Allocation Unit Size:
Optimal
values
64Kb*
64Kb
OS CONFIG
* Defined by storage team.

43. Example:
Stripe Unit Size:
Allocation Unit Size:
Optimal
values
64Kb*
64Kb
Data (Alloc. Unit Size)
OS CONFIG
Stripe Size
* Defined by storage team.

44. Optimal solution:
Data (Alloc. Unit Size)
Stripe Size
OS CONFIG

45. Best Practice:
- Set an offset of 1024 Kb.
-
This value works for mostly disks out there.
- Allocation Unit Size = Stripe Unit Size.
The rule:
Offset / Allocation unit = INTEGER
Eg: 1024/64=16
OS CONFIG

46. WARNIG
Some I/O subsystem vendors intercepting what
Windows is trying to do and are still creating
partitions with the incorrect offset – Even for
Windows 2008+.
ALWAYS check!

47. Anti-Virus
servers…
is really a need?
OS CONFIG
in

48. •
•
•
•
Cost money to license.
Maintenance costs.
Can cause problems in Prod.
Can’t protect to zero-day exploits.
OS CONFIG

49. What can we do instead?
OS CONFIG

50. •
•
•
•
Keep the servers patched.
Configure the firewall properly.
Restrict server’s access.
You can install AV… in workstations!
OS CONFIG

51. What’s the big problem for
SQL Server?
OS CONFIG

52. • One more app fighting for resources.
• SQL Server files can be locked.
OS CONFIG

53. How can AV and SQL Server
live together?
OS CONFIG

54. Add exceptions!
OS CONFIG

55. Basically the AV should ignore:
•
•
•
•
•
•
•
SQL Server data and log files (.mdf, .ndf and .ldf).
Backup files (.bak and .trn).
Full-text Catalog files.
Trace files (.trc).
ERRORLOG files.
SQL Server binaries folder.
Filestream folder.
OS CONFIG
More on: http://support.microsoft.com/kb/309422

56. INSTANCE CONFIG

57. Memory
INSTANCE CONFIG

58. Memory
This is a very open subject.
INSTANCE CONFIG

59. Memory
This is a very open subject.
There are lots of discussions about that…
INSTANCE CONFIG

60. Memory
This is a very open subject.
There are lots of discussions about that…
There’s no perfect formula, because the correct awnser is….
INSTANCE CONFIG

61. Memory
This is a very open subject.
There are lots of discussions about that…
There’s no perfect formula, because the correct answer is….
… it depends !!
INSTANCE CONFIG

62. Memory
An efficient general rule…
Baseline: 1 GB for the OS
Up to 16 GB available
• 1 GB for each 4 GB
More than 16 GB
• 1 GB for every 8 GB
INSTANCE CONFIG

63. Memory
This is for 64 bit servers…
For 32 bit, here is a good article to follow:
http://www.eraofdata.com/understanding-and-configuring-sql-servers-memory-settings/
INSTANCE CONFIG

64. TempDB
INSTANCE CONFIG

65. TempDB
Two common behaviors:
INSTANCE CONFIG

66. TempDB
Two common behaviors:
• Ignore.
• Overvalue.
INSTANCE CONFIG

67. TempDB
As per Brent Ozar:
“TempDb is the SQL’s public
toilet”
INSTANCE CONFIG

68. TempDB
And this is
true!
INSTANCE CONFIG

69. TempDB
INSTANCE CONFIG

70. TempDB
There’s a myth:
• tempdb should always have one data file per processor core.
INSTANCE CONFIG

71. TempDB
There’s a myth:
• tempdb should always have one data file per processor core.
Again….
INSTANCE CONFIG

72. TempDB
There’s a myth:
• tempdb should always have one data file per processor core.
Again…. It depends!
INSTANCE CONFIG

73. TempDB
Execute large operations, like a sort or store a huge temporary table,
may be slowed down because of the round-robin operation.
The more files, the more costly.
INSTANCE CONFIG

74. TempDB
Common wait types on TempDB:
• PAGELATCH_*: Contention for In-memory allocation bitmaps.
• PAGEIOLATCH_*: Contention at the I/O subsystem level.
INSTANCE CONFIG

75. TempDB
How many tempdb data files should we have?
INSTANCE CONFIG

76. TempDB
How many tempdb data files should we have?
A recommended approach is:
• Up to 8 cores:
Number of files = Number of cores.
• More than 8 cores:
1. Add 8 files.
2. Monitor PAGELATCH_*.
3. Add 4 more files at a time, if necessary.
INSTANCE CONFIG

77. TempDB
Other TempDB best practices:
• Isolate the TempDB in a different storage system.
• Depending of the load, you might need to separate LDF
and M(N)DF.
• Use a fast drive (SSD :).
• Set an initial size, equally to all the files.
• Set the auto-growth accordingly.
• If you have a heavy operation using constantly the
TempDB, consider create a staging table into your own
database.
INSTANCE CONFIG

78. TempDB
From SQL Server 2012, local disk TempDB in SQL
Server cluster.
INSTANCE CONFIG

79. TempDB
From SQL Server 2012, local disk TempDB in SQL
Server cluster.
• More flexibility.
• Use PCIe bus instead of HBA, and have more throughput.
• Data and Log are in SAN, TempDB locally: Avoid
congestion or contention on a shared storage network or
array.
INSTANCE CONFIG

80. DB CONFIG

81. • Don’t rely on auto-grow.
• You can manage file growth and control the free
disk space and avoids performance problems.
DB CONFIG

82. • Don’t rely on auto-grow.
• You can manage file growth and control the free
disk space and avoids performance problems.
• Have page checksums turned on.
• To detect damaged pages.
DB CONFIG

83. • Don’t rely on auto-grow.
• You can manage file growth and control the free
disk space and avoids performance problems.
• Have page checksums turned on.
• To detect damaged pages.
• Make sure auto-stats update is turned on.
• For OLTP consider turning auto-stats update off
only for heavily updated tables, and schedule a
job that periodically updates the statistics for
those tables.
DB CONFIG

84. DB CONFIG

85. • Make sure you’re managing the transaction log
correctly:
• Full recovery requires log backups.
• No advantage in have multiple log files.
• Control the file growth or this could cause
VLF fragmentation.
• Performance issues.
• Slow backup time.
• Don’t set the log file growth size to a multiple of 4 in
older SQL Server versions.
•
http://connect.microsoft.com/SQLServer/feedback/details/481594/log-growth-not-workingproperly-with-specific-growth-sizes-vlfs-also-not-created-appropriately
DB CONFIG

86. MAINTENACE

87. Few questions…
MAINTENANCE

88. How to meet your SLAs dealing with a TB database?
Is data-loss acceptable?
What about the recovery time?
Are you able to UPDATE STATS, do INDEX MAINTENANCE
and run a INTEGRITY CHECK in time and WITHOUT PROBLEMS?
MAINTENANCE

89. DISASTER RECOVERY
MAINTENANCE

90. First of all, think in a Disaster Recovery plan!
SQL Server is not Oracle, we have “free” included options:
• Log Shipping (HA and DR)
• Database Mirroring (HA and DR)
•
DB Snapshot advantage
• Replication (HA, DR and LB)
• AlwaysOn (HA, DR and LB)
• We can still be safe with a storage level replication.
MAINTENANCE

91. Partition
Compress
Clean
MAINTENANCE

92. Partition, Compress and Clean
Using the partitioning feature you can devise the maintenance.
MAINTENANCE

93. Partition, Compress and Clean
Using the partitioning feature you can devise the maintenance.
• You can use the DBCC CHECKFILEGROUP command.
•
DBCC CHECKFILEGROUP and DBCC CHECKDB are. The main difference
is that DBCC CHECKFILEGROUP is limited to the single specified filegroup
and required tables.
MAINTENANCE

94. Partition, Compress and Clean
Using the partitioning feature you can devise the maintenance.
• Devising a filegroup architecture allows piecemeal restores
with low TTR
• Online piecemeal restore:
•
•
After the PRIMARY FG restore the DB can be online.
The tables will come available while each FG is restored.
• Design the database accordingly:
•
•
Keep the necessary into the PRIMARY FG.
• Configuration tables, indispensable data, etc…
Think in the consistency: keep related tables in the same FG.
MAINTENANCE

95. Partition, Compress and Clean
Compress backups Vs. Compress Data
• Backup compression:
• More CPU usage to backup/restore (avg ~20%).
• Less time to backup/restore (avg ~40%).
• Good compression ratio.
•
SELECT backup_size/compressed_backup_size FROM msdb..backupset;
• A backup set will not be able to contain both compressed
and uncompressed backups.
• No advantage with TDE enabled.
MAINTENANCE

96. Partition, Compress and Clean
Compress backups Vs. Compress Data
• Data compression (ROW and PAGE):
• TDE and Data Compression play together!
• Backup and Data Compression can coexist!
MAINTENANCE

97. Partition, Compress and Clean
Purge and Archive the data
• Purging data:
• If data is needed no more…
• Save storage.
• Faster backups.
• Improves the performance.
MAINTENANCE

98. Partition, Compress and Clean
Purge and Archive the data
• Archiving data:
• If data is still needed…
• Isolate in a different FG.
• Set as Read-Only: Avoids locking.
• For faster scans: 100% fill factor.
• Update statistics with FULLSCAN.
• You can adapt the backup strategy.
• You can adapt the backup strategy using Partial Backups.
MAINTENANCE
•
This allows you to exclude read-only filegroups.

99. More about DBCC CHECKDB
• CHECKDB takes time and uses resources.
• Run a DBCC CHECKDB using the WITH PHYSICAL_ONLY option.
•
•
Limits the checking to the integrity of the physical structure of the page
and record headers and the allocation consistency of the database.
Faster, but a full CHECKDB is required periodically.
MAINTENANCE

100. More about DBCC CHECKDB
• We can divide up the consistency checking over several days, Paul
Randal’s prescription is:
•
Divide tables in two buckets (bigger ones and the rest)
• On Sunday:
• Run a DBCC CHECKALLOC
• Run a DBCC CHECKCATALOG
• Run a DBCC CHECKTABLE on each table in the first bucket
• On Monday, Tuesday, Wednesday:
• Run a DBCC CHECKTABLE on each table in the 2nd, 3rd, 4th
buckets, respectively
• On Thursday:
• Run a DBCC CHECKALLOC
• Run a DBCC CHECKTABLE on each table in the 5th bucket
• On Friday and Saturday:
• Run a DBCC CHECKTABLE on each table in the 6th and 7th
buckets, respectively
MAINTENANCE
More on: http://www.sqlskills.com/blogs/paul/checkdb-from-every-angle-consistency-checking-options-f

101. More about BACKUPS
• Besides doing PARTIAL BACKUPS we have more options…
• A MULTISTREAM BACKUP is an option to run faster:
File 1
File 2
F:
File 3
DB
E:
G:
MAINTENANCE

102. More about BACKUPS
• To make sure it will be well stored, we can use a MIRROR.
File 1
File 1
File 2
File 3
DB
E:
File 2
F:
File 3
G:
MAINTENANCE

103. More about BACKUPS
• If storing to the network:
• Use a separate network card to avoid network congestion.
• Don’t forget about T-LOG backups!
• Create a good backup strategy.
• Verify the backups periodically.
MAINTENANCE

104. INDEXES MAINTENANCE
• Only rebuild/defrag indexes that are really fragmented (avoid
unnecessary work in short maintenance windows)
• If you defrag instead of rebuild, make sure you manually update
stats.
• Be wary of doing large index maintenance jobs if you use log
shipping or DBM
• They contribute to large log backups
• Index rebuilds are always full-logged when DBM is present
MAINTENANCE

105. QUESTIONS?

106. OBRIGADO!
@murilocmiranda
http://www.sql.pt/
murilo.miranda@gmail.com