disk defragmentation and DisKeeper

GeneO · 22 Aug 2011

maxseven said:

This is all pretty mysterious, and frankly appalling if MS Defrag itself has potential to destroy Restore Points--a lot of people (myself included) rely on these. I think in the Piriform forum was referred http://support.microsoft.com/kb/312067 wherein is stated the following:

The System Shadow Copy provider uses a copy-on-write mechanism that operates at a 16-KB block level. This is independent of the file system's cluster allocation unit size. If the file system's cluster size is smaller than 16 KB, the System Shadow Copy provider cannot easily determine that disk defragmentation I/O is different from typical write I/O, and performs a copy-on-write operation. This might cause the Shadow Copy storage area to grow very quickly. If the storage area reaches its user-defined limit, the oldest shadow copies are deleted first

It's from 2007, and at top it says "may not apply to your OS" (W7 running here).

So I'm not sure what to think about all this because it seems that if the simple solution were to stop the Volume Shadow Copy service, run the defrag, then restart VSCS, well Piriform would have incorporated this already?

EDIT: Oops here's another quote about Vista (VSS aware):

In shadow-copy-aware defragmentation, defragmentation uses Volume Shadow Copy Service (VSS) in-box software to optimize defragmentation. The VSS software minimizes copy-on-write change blocks. Shadow-copy-aware optimization slows down filling the difference area. This kind of optimization also slows down the reclaiming of old snapshots during defragmentation.

So maybe this is not so mysterious after all, unless Piriform hasn't figured this out yet.

Windows 7 defragmenter is optimized to minimize any adverse affects on VSS.

GeneO · 22 Aug 2011

karlsnooks said:

gene,
For Windows Vista, then one must be cautious.

I have posted a question in their forum re Defraggler and Win 7. I have not received an answer.

If you can get a direct answer from Piriform directly on this matter, then I'd be grateful.

As said for Vista, true, but I've not found a statement re Win 7.

I believe Windows 7 = Vista (or better) in this respect.

Cheers

**cluberti** · 22 Aug 2011

Any program that moves large numbers of files around disk in a short amount of time is going to cause some (or more) destruction of VSS stored data, due to the way this looks to the OS (oh, some program needs a ton of space - free up volume shadow copies and mount points to make that space available post haste!). Defragmenters that are spartan about moving actual files around unnecessarily can avoid this (especially if they avoid large files, like the inbox defragmenter does), but this means potentially less defragmenting done to the drive itself. It's a tradeoff - have great file structure for head reads/writes, or leave a bit of fragmentation (define "a bit"

) and don't go whacking a ton of mount points.

You get to choose one or the other, but not both, at least not on a running system.

maxseven · 23 Aug 2011

GeneO said:

Windows 7 defragmenter is optimized to minimize any adverse affects on VSS.

cluberti said:

Defragmenters that are spartan about moving actual files around unnecessarily can avoid [problems](especially if they avoid large files, like the inbox defragmenter does), but this means potentially less defragmenting done to the drive itself.

Well, I wonder if Piriform doesn't use the W7 defragger already. It seems to me that I've used Defraggler a couple times and

1. Not noticed any problems from its use, and

2. Observed that it didn't completely defrag my volume either

I have a W7 PC with an SSD (bad to defrag! don't do it!) and a couple others with spinners and I'm gonna stick with W7 built-in defrag for the time being...

**cluberti** · 23 Aug 2011

Well, the APIs to use for defragmentation are pretty well documented, as is the way VSS works when you move around lots of files in short order (KB article). It's not surprising that they could put 2 and 2 together

. Using VSS is also documented, so there are other ways to handle this as well - none of them are perfect, of course, but there are possibilities.

karlsnooks · 23 Aug 2011

OK guys, I mentioned it before. I suggest you use Contig. Check the thread where I showed how to use it.

Safe and effective defrag.

DBone · 23 Aug 2011

It doesn't just have a defrag button??

scr · 24 Aug 2011

DBone said:

It doesn't just have a defrag button??

It's a command line tool.. more info: Contig

karlsnooks · 24 Aug 2011

DBone said:

It doesn't just have a defrag button??

See post #4 in this thread.