MyD 431 SkipBlock?

[Gurky42]

I was looking at the 'SkipBlock' option and was wondering if anyone has actually used it. If so, can anyone explain exactly what this is supposed to do in a more dumbed down fashion. I've read the help file description more times then I care to admit, and I still can't wrap my head around just what its intended to do.

I noticed this:

This is a huge timesaver in cases where there has been only a small change in the zone, for example a single file that was added or deleted.

If this is the case, then why isn't this option being used in the default scripts?

And before anyone says "Just try it and see", I'm not due for a monthly style defrag/optimize for at least another week or so. So no, I'm not going to change my scripts and wait around to see what this does to my files just for the fun of it. Since its newly added, is it experimental or what? Is there a downside to using the option (hence the reason it isnt in the default scripts)?

Thanks,

[Darlis]

I haven't used it myself and don't think it is experimental. I guess the answer would be that the general user wants a complete optimization. At least thats the reason for sorting the spacehogs in the monthly system disk script.

[Bibby]

I have used the following:

  FileActions
    SortByName(Ascending SkipBlock(2,ZONE222N * 0.001))
  FileEnd

I find it does indeed speed things up. The only thing i have noticed however is that it produces many wrapped-around fragmented files.

I'm not absolutely certain but I think it causes files to wrap around a whole block (block defined in the line "SkipBlock(2,ZONE222N * 0.001)"). The problem here is that if the block is large then the fragments can be too far apart.

[jeroen]

Since its newly added, is it experimental or what?

It is a new option, not experimental. It has just not extensively been tested yet. I would like to hear from everybody what they think of it, how it is performing, if they find any problems.

[jeroen]

The only thing i have noticed however is that it produces many wrapped-around fragmented files.

I have looked at the sources and now I see that this is indeed what happens. It did not show up in my own tests, I wonder why. It's not what I want.... I will have to think about it.

[poutnik]

Skipblock intention is to prevent sorting already sorted parts of sorted zone ( even if they lays on suboptimal place ). If it finds a continuous block of already sorted files,  it checks if the block has minimal file count and block size. If it has, then skipblock internally considers the block as unmovable, being sorted already. All rest files from zone are then sorted in areas, that do not belong to any skipped block, wrapping eventually these blocks.

Such settings reminds me my previously suggested "iceberg" approach of sort preservation, ( considering such a block being a single file )
intended for FastFill modification, that would not have problem with block - iceberg wrapping and file fragmentation.

Side effect of Skipblock wrapping is obvious. Further analysis will mark wrapped around files as fragmented, because wrapped blocks are movable again.

I was trying recently SkipBlock feature on boot zone sorted by layout.ini order.
My idea was to tame sorting to be usable on my custom daily till weekly script.

I have realized even at daily runs it sorted very most of boot zone, until I went down with SkipBlock parameters to 3-10 files and 64-512 kB.
Such extreme settings obviously lead to heavy block wrapping fragmentation, leading in fact to file placement deoptimization.

For standard script "middle zone" of used files the SkipBlock was more friendly and SkipBlock parameters can be increased, but not much.

[Bibby]

Another problem I have noticed is that with skipblock the zone has gaps. Normally the SortBy method fills everything in leaving no gaps.

[poutnik]

Another problem I have noticed is that with skipblock the zone has gaps. Normally the SortBy method fills everything in leaving no gaps.

It happens when sortby would like to shrink zone.
But it  cannot because it has decided previously not to touch Skipblocks.