Defragmentation leaves gaps between blocks

[flahmeshess]

When I use WinXP to do a defrag of the harddisk, it leaves gaps in
between blocks. This would encourage future files to be defrag. Is
WinXP / Win2000 able to close these gaps ? Or must I purchase an
utility to do that ? Thanks.

 

[Bjorn Landemoo]

This is a function built in to the NTFS file system, in order to let a file
grow slightly without being fragmented. Removing the gaps might actually
increase fragmentation. In order to avoid this function you would need to
select another file system, FAT or FAT32.

As long as you never fill an NTFS volume entirely, the unused gaps will not
be filled with other files.

Best regards

Bjorn

 

[Greg Hayes/Raxco Software]

Leaving free space "holes" isn't a function of NTFS - it is a function of
whatever defragmenter is being used? Lack of free space consolidation
actually results in wasted seeks and a degradation of hard drive
performance. It is possible to consolidate free space - however, this isn't
something that the built-in defragmenter is particularly good at doing.

- Greg/Raxco Software
Microsoft MVP - Windows File System

Disclaimer: I work for Raxco Software, the maker of PerfectDisk - a
commercial defrag utility, as a systems engineer in the support department.

Want to email me? Delete ntloader.

 

[George Hester]

The best one in that regard I believe is Norton's. No longer available.

 

[Michael D. Ober]

From observation, Executive Software's Diskeeper will leave the gaps when
defragging in background. However, it will close them if you do a manual
defrag. My recomendation is to do a manual defrag after you install the OS,
any major applications or OS upgrade, and if you really need large amounts
of consolidated free space. The rest of the time do background defrags and
don't worry about these holes. A scaled down version of Diskeeper Lite is
what MS incorporated into Windows 2000, XP, and 2003.

Greg, can you post a comparison for us on how Raxco's PerfectDisk handles
this? Also, what "system" files can PerfectDisk defragment, both on-line
and at boot-time?

Mike Ober
Diskeeper Customer only

The best one in that regard I believe is Norton's. No longer available.

 

[Greg Hayes/Raxco Software]

Mike,

Actually, if you look at the Diskeeper documentation, Diskeeper provides an
"Improved Free Space" consolidation defrag method. However, you can't
manually defrag using Improved Free Space method - it can only be scheduled
and occurs slowly as it is used over time - which means that it isn't very
effective.

If you visit the Raxco web site, you can find information/comparisions. You
might want to read the study on free space consolidation at and how NOT
doing it actually results in wasted seeks and a reduction in drive
performance.

PerfectDisk's boot time defrag is used only to defragment those files that
Microsoft's defrag API do not support defragmenting online. This includes
the pagefile, hibernate file directories on FATx drives and NTFS metadata
($MFT, etc...) All other files can usually be defragmented online -
including SQL database devices and Exchange datastores.

- Greg/Raxco Software
Microsoft MVP - Windows File System

Disclaimer: I work for Raxco Software, the maker of PerfectDisk - a
commercial defrag utility, as a systems engineer in the support department.

Want to email me? Delete ntloader.

 

[Michael D. Ober]

Greg,

Good points, except that the Diskeeper documentation is misleading about the
manual defrag. Although you don't have the "improved free space" option,
doing a manual defrag actually moves all the files as close to the front of
the disk as possible without entering the MFT. What you probably don't know
is that Diskeeper won't defragment the Metadata files such as the hibernate
file - it's even in their FAQ it says that certain system files cannot be
defragmented because NTFS maps them at startup and requires they not be
moved for file system integrity reasons. The documentation doesn't say
which files these are, however.

As for PerfectDisk 7, I just had a server that had an extremely fragmented
metadata file (over 5000 excess fragments) and Diskeeper wouldn't touch it,
even at boot time. The largest contiguous block of free space was less than
50 Mb on an 18Gb disk that was only half full. I downloaded the trial
version of PerfectDisk 7, deinstalled Diskeeper and installed PerfectDisk.
Then I did an on-line defrag followed by a boot time defrag and PerfectDisk
and it defragged the MetaData, saving me a weekend's worth of rebuild.
Needless to say I have now put on our purchase list for this year
PerfectDisk Server for our servers. We're small enough that my assistant
identifies the workstations needing defragged using a network fragmentation
analysis tool and goes and defrags the two or three workstations each month
that need defragging.

Also, can you feed back that the Defrag API needs to be fixed to avoid the
problems listed in KB 282791, "FRS: Disk Defragmentation Causes Excessive
FRS Replication Traffic". I believe this was the cause of my our Metadata
fragmentation problems. Basically, the Defrag API needs to mark the USN
journal in such a way that the FRS service won't try to replicate a
defragged file.

Thanks,
Mike.