Transcript Improving File System Performance

Windows File Systems and
Improving Performance
APCUG
1/5/2008
Greg Hayes
Raxco Software
[email protected]
Introduction
• Company Background
– Raxco founded 1978
– Largest provider of OpenVMS system
management software
– Spun off Axent Technologies (now part of
Symantec) in 1996
– First Windows product released in 1998
Introduction
• Company Background
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Microsoft Gold Certified Partner
Microsoft ISV
Member of Microsoft Development Network
Software used by some of the largest
companies and government organizations in the
world
Introduction
• Speaker background
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System manager for 10+ years
Raxco customer for 10 years
Started at Raxco in 1996
Manager, Technical Solutions
Microsoft MVP 2003-2007 - Windows File Systems
Online communities
Speaking/Education
Topic Background
• Who remembers their first PC?
• PC hardware performance continues to rise
– CPU clock speeds > 2Ghz
– 2GB RAM
– 500GB+ capacity hard drives
• Limiting factor is still disk I/O
• Anything that speeds up access to disk
improves performance
Windows File
Systems
• FAT16
• FAT32
• exFAT (new)
• NTFS
Windows File Systems
• FAT16/32
The File Allocation Table is created when you
format a FAT drive and contains
information about all of the files found on
the drive and where they logically reside.
There are actually 2 FATs per partition.
Windows File Systems – FAT16
• Benefits:
– Faster performance on smaller partitions - less
than 4GB
– Best Performance for Pagefile
• Drawbacks:
– Little or no security
– High rate of file system corruption
– Limits on partition size (FAT16 – 4GB)
Windows File Systems – FAT16
• FAT16
– 4GB FAT16 partition has a cluster size of 64k.
– Wastes space as even the smallest files take up
a full cluster.
– Maximum file size is 2GB
– Files per volume 65,536
Windows File Systems – FAT32
• FAT32
– Maximum file size is 4GB
– Allows smaller cluster sizes to be used –
resulting in less space “waste”
– Maximum partition size is 32GB (as formatted
by XP/Vista/2K3)
– Up to 2TB can be written/read (XP/Vista/2K3)
– Files per volume ~4,177,920
Windows File Systems – exFAT
• exFAT
– “Extended FAT”
– Designed for flash media – exchange media
with PCs.
– Free space bitmap for faster allocation
– Maximum theoretical file size is 16EB
– More than 1000 files per folder
Windows File Systems - NTFS
• Journaling/Transaction Based File System
• “Self Describing” File System
• Metadata - data that describes data
Windows File Systems - NTFS
• Benefits:
– Better security
– Better performance with large partitions –
greater than 4GB
– Better resistance to file system corruption
• Drawbacks:
– Can’t natively boot to MSDOS and get access
to partition
Windows File Systems - NTFS
• NTFS
– Maximum file size is approx 16TB
– Maximum partition size is 2TB – 256TB
(depends on cluster size used)
– Files per volume 4,294,967,295
Windows File Systems - NTFS
• NTFS
– Disk Quotas (Win2K and newer)
– File/Folder compression built into the file
system
– Encryption built into the file system (Win2K
and newer)
– Volume Shadow Copy (VSS – WinXP and
newer)
– txNTFS
NTFS Metadata
• $MFT - Master File Table (0)
– The $MFT contains at least 1 record for each
file that exists on the partition.
• $MFTMirr – Master File Table Mirror (1)
– Duplicate of the 1st 4 records of the $MFT
– Used for redundancy/recoverability
NTFS Metadata
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$LogFil – NTFS Transaction Log (2)
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Updates to the file system first get posted to
the transaction log
Gives NTFS its “self-healing” abilities
$Volume – Volume Information (3)
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Volume Label/Version
NTFS Metadata
• $AttrDef – Attribute Definitions (4)
– Names, Numbers, Descriptions
• $Root – (5)
– Root folder on the drive. (I.e. C:\)
NTFS Metadata
• $Bitmap – Cluster Bitmap (6)
– Indicates whether a cluster is used or empty
– Uses this to quickly find free space
• $Boot – Partition Boot Sector (7)
– Location of the partition boot sector
– Bootstrap loader code if bootable drive
NTFS Metadata
• $BadClus – Bad Cluster File (8)
– Clusters the file system has reported as bad
– Updated by CHKDSK
• $Secure – Security Descriptors (9)
• $Upcase – Upcase Table (10)
– Translation of lowercase characters to their equivalent
Unicode upper case characters
NTFS Metadata
• $Extend – Optional Extensions (11)
– User Change Journal
– Quotas
Anatomy of a $MFT Record
• Fixed size records – 1K
• Attribute Records
– $FILE_NAME
• 8.3 file name and parent directory
• Long File Name
– $DATA
• Extent information for file. Includes Logical Cluster
Number (LCN) and Run Length
• $DATA record contains information on file size
Anatomy of a $MFT Record
• DiskEdit
MFT Reserved Zone
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Created when partition is formatted
$MFT will “grow into” as needed
File system will keep free if possible
Defragmenters can not use free space inside
of MFT Reserved Zone (NT4/Win2K)
MFT Reserved Zone
• NT4
– Fixed Size
– 12.5% by default
– Can be increased up to 50% via registry key
MFT Reserved Zone
• Windows 2003/2000/XP/Vista/2008
– Dynamically created every time partition is
mounted
– First record of $MFT to first non-free cluster up to a default max of 12.5%
Logical vs Physical Clusters
• Logical Clusters
– File system level
– Every partition starts at logical cluster 0
– No idea of hard drive technology in use
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IDE
SCSI
RAIDx
# platters or read/write heads
Logical vs Physical Clusters
• Physical Clusters
– Hard drive level
– Hard drive controller translates logical-tophysical and positions heads
Application
Requests
File
O
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Logical ClusterView
File System
Disk Controller
Disk
Disk
Physical ClusterView
Disk
Cluster Size and Performance
• Smaller clusters
– less wasted space
– Worse performance – especially large files
• Larger clusters
– more wasted space
– Better performance – especially large files
Conversion from FATx to NTFS
• NT4/Win2K
– Results in 512byte clusters
– Not “the best” for performance - especially
with video/image applications
• WinXP/Vista
– Will try to convert using 4k clusters.
– Best for general file system performance.
OEM Vendors and Cluster Size
• IBM/Dell/HP
– Provide Software to install/configure Windows
Server
– Formats system drive with 512byte cluster
– Absolute worse for system drive performance
– Only way to convert is 3rd party tools and have
server unavailable for extended period
(HP SmartStart, Dell OpenManage, IBM ServerGuide)
Biggest Cause of Poor File
System Performance
• Fragmentation!
Fragmentation Causes
• What causes fragmentation?
– Occurs when files are created, extended or
deleted
– Happens regardless of how much free space is
available (After XP/SP2 installation – 944
files/2943 fragments)
– More than one Logical I/O request has to be
made to the hard drive controller to access a file
Fragmentation Impacts
• What does fragmentation do to my system?
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Slows down access to files
Extra CPU/Memory/Disk resource usage
Some applications may not run
Slow system boot/shutdown
Audio/Video record/playback drops frames or
“skips”
Measuring Impact of
Fragmentation
• Measuring the performance loss in reading
a fragmented file
What Can I Do About
Fragmentation?
• You can’t stop fragmentation from
happening (you can only slow it down)!
• What you CAN do is to defragment
Defragmenting - Results
• What does defragmenting do?
– Locates logical pieces of a file and brings them
together
• Faster to access file and takes less resources
• Improves read performance
– Consolidates free space into larger pieces
• New files get created in 1 piece
• Improves write performance
Measuring Impact of
Fragmentation
• Measuring the performance difference in
reading a contiguous file
Defragmenting - Issues to
Consider
• Safety, Safety, Safety!
– No loss of data
– No corruption of data
Defragmenting - Issues to
Consider
• Free Space
– How much is enough?
– Where is free space located?
• Inside MFT Reserved Zone
• Outside of MFT Reserved Zone
– Consolidation of free space
Safety - Microsoft’s Defrag APIs
• Provided as part of the operating system
• Defragmenters do not actually move files
• Integrated with caching system and
Memory Manager
• Performs all I/O synchronization
• Allows even files in use to be defragmented
Safety - Microsoft’s Defrag APIs
• Restrictions
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Move Granularity
Free Space in MFT Reserved Zone
NTFS Cluster Size
Special OS files
• Pagefile
• Hibernate file
• NTFS Metadata
Microsoft’s Defrag APIs
• “Quirks”
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Compressed files (NT4/Win2K)
File System Cache (NT4/Win2K)
Encrypted Files (Win2K)
NTFRS/DFS (Win2K)
VSS (Vista,Win2K3)
Free Space Consolidation
• Allows new files to be created contiguously
– Maintains file system performance longer
– Requires less frequent defrag passes
Free Space Consolidation
• Defragmenting files improves read
performance
• Free space consolidation improves write
performance
Single Pass Defragmentation
• As my dad always told me…
– If you are going to do a job – do it right the first
time
• After defrag has completed, you don’t have
to “wonder” if you need to run again
• Fragmentation issue is solved – done!
File Placement Strategy
• When you play chess, do you have a
strategy or do you just start moving pieces
around?
• A good file placement strategy
accomplishes several things:
– Slows down re-fragmentation
– Speeds up future defrag passes
– Works with the operating system – not against
Windows Prefetch
• What is Prefetching?
– Windows monitors system boots and
application launches
– Uses information gathered to perform driver
load optimization (speeds up boot process)
– Uses information gathered to speed up
application launches
Windows Prefetch
• Windows stores this information in the
\Windows\Prefetch folder
– Layout.ini
– Xxxx.pf
• Every 3 days, Windows will automatically
perform a “partial” defrag of the files
indicated in layout.ini
Windows Prefetch
• This process depends on a large enough
piece of contiguous free space being
available. If there isn’t, then it doesn’t
happen!
Windows Prefetch
• Defragmenters - working WITH the
operating system NOT against. Microsoft
says:
– Either respect where Windows places these files
OR
– Manage these files yourself
“Tweaking” - BootVis
• BootVis
– One of the most mis-understood “tweaking”
tools around
– Available from Microsoft
– Used to profile system boots
• Optimize driver loading for faster boots
• Calls built-in defragmenter to “optimize” boot files
• Also can be used to identify drivers that load slowly
“Tweaking” - BootVis
• Windows XP does this boot optimization
over a period of boots (after 3 boots have
been performed)
• BootVis does it “now”
• End result is the same
“Tweaking” – Disable Last Access
• HKLM\System\CurrentControlSet\Control\
FileSystem\Disablelastaccess =1
• Improves NTFS performance by 2%
• Last Access updating turned off by default
in future versions of NTFS (2008 Server)
“Tweaking” – 8.3 Name Creation
• Win2k3/XP/Vista: fsutil.exe behavior set
disable8dot3 1
• Win2k:HKLM\System\CurrentControlSet\C
ontrol\FileSystem\NtfsDisable8dot3NameC
reation = 1
• Provides faster directory enumeration
• Legacy apps may no longer install/work.
“Tweaking” – Purging Prefetch
• Belief is that a large number of entries in
layout.ini slows down system.
• Windows will manage effectively. Use of
entries in layout.ini actually speeds up
system boots and application launch.
“Tweaking” – Disabling Vista’s
SuperFetch
• Belief is that not having a large amount of
free memory available is a bad thing.
• SuperFetch caches frequently accessed
programs/data and uses available RAM.
Unused RAM is a wasted resource.
• SuperFetch survives system restarts. XP
caching doesn’t.
Volume Shadow Copy (VSS)
• VSS and defragmentation
• Multiple of 16k cluster size
• Default cluster size is 4k because NTFS
compression hasn’t been modified to
support greater than 4k cluster size.
• BitLocker (Vista) also restricted to 4k
cluster size
DiskPar/DiskPart
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DiskPar - Win2k
DiskPart – Win2k3
Want to avoid crossing track boundaries
Align on 64k for best MS SQL performance
Win2k8 – default is 64k when creating
volumes
• Contact storage vendor – i.e. EMC
recommends 64k
Disk Technology
• SATA worse in high write environments –
however cheap
• RAID1+0 best for high read/write
environments AND redundancy – however
expensive
• More onboard cache – better performance
Performance Measuring Tools
• Windows Performance Monitor
– Split I/O Count (fragmentation)
– Disk Queue Length (<= 2/spindle)
• hIOMon – www.hiomon.com
– Device AND File based metrics
• SQLio – Microsoft
– Stress Test I/O subsystem
Cluster Size Recommendations
Drive Use
Windows OS
File
System/Cluster
Size
Notes/Considerations
NTFS - 4k (Default)
File Server general Office data NTFS - 16k
Databases
NTFS - 64k
Exchange
NTFS - 64k
Need to also have pagefile on OS drive
if you want to capture memory dump on
Windows crash.
Windows 2003/2008/Vista - minimizes
shadow copy/Restore Point purges.
For Windows 2000, use 4k.
Windows 2000, use 4k.
Windows 2000, use 4k.
Virtual - VHD/VMDK NTFS - 64k
Video/Graphics
NTFS - 16k
Windows 2000, use 4k.
Windows 2000, use 4k.
Pagefile (separate
physical drive)
FAT32
* You can’t use compression if cluster size greater than 4k
Conclusion
• To improve file system/drive performance
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Use appropriate disk technology
Use the most appropriate file system
Use the most appropriate cluster size
Align on cluster boundaries
Make sure free space is consolidated
When you defragment, make sure that it is
being done effectively.
Conclusion
Questions/Answers