Fine sector adjustment on existing partition

[rcebolleto]

Ok, so I'm trying to optimize some servers that all have the 63 sector
(32256-byte) partition offset instead of the true 64 sector (32768-byte)
offset. Normally when I prep a server, particularly an Exchange of
VMWare (on windows) box, I use Diskpar to create my true 32k offset
partitions to minimize sector-boundary overlaps in the disk cache and
possibly on the actual writes.

However, I am working on some machines that have already been prepped -
OS loaded, all apps, all GPO's and AD and everything else. I'd rather
not format and redo the entire job if it can be avoided - I just want to
'nudge' the entire partition up one sector into alignment. However, all
of the partition tools I have played with (all the major ones like PM,
Acronis, Norton) deal in much, much larger chunks than a single sector -
they only adjust partitions several megabytes at a minimum. They clearly
are just designed for reorganizing space on a macro scale, not fixing
sector alignment issues.

I also tried getting clever about it and fooling with a hex editor and
dd (on a test drive, not on anything important) and *almost* got what I
wanted but I keep running into problems getting the bootloader to find
NTLDR or with NTFS not finding any files in the directory, or only some
of them, or worse. So before I dig into this again and kill another
weekend trying to figure out how to hand-craft the MBR, PBR, volume
extents and whatever else to make this work, I was wondering if anyone
heard of a tool that does this job?

THX!

 

[Arno Wagner]

Ok, so I'm trying to optimize some servers that all have the 63 sector
(32256-byte) partition offset instead of the true 64 sector (32768-byte)
offset. Normally when I prep a server, particularly an Exchange of
VMWare (on windows) box, I use Diskpar to create my true 32k offset
partitions to minimize sector-boundary overlaps in the disk cache and
possibly on the actual writes.

However, I am working on some machines that have already been prepped -
OS loaded, all apps, all GPO's and AD and everything else. I'd rather
not format and redo the entire job if it can be avoided - I just want to
'nudge' the entire partition up one sector into alignment. However, all
of the partition tools I have played with (all the major ones like PM,
Acronis, Norton) deal in much, much larger chunks than a single sector -
they only adjust partitions several megabytes at a minimum. They clearly
are just designed for reorganizing space on a macro scale, not fixing
sector alignment issues.

I also tried getting clever about it and fooling with a hex editor and
dd (on a test drive, not on anything important) and *almost* got what I
wanted but I keep running into problems getting the bootloader to find
NTLDR or with NTFS not finding any files in the directory, or only some
of them, or worse. So before I dig into this again and kill another
weekend trying to figure out how to hand-craft the MBR, PBR, volume
extents and whatever else to make this work, I was wondering if anyone
heard of a tool that does this job?

Quite frankly, I don't think what you are doing will result
in a measureble speed improvement. I think you are wasting
your time. Maybe you shpould first determine if your assumptions
are correct and then invest effort in doing this ''optimization''.

Arno

 

[rcebolleto]

What do you think of this, then:

http://geekswithblogs.net/ntpro/archive/2005/08/11/49948.aspx

and this

http://lonesysadmin.net/2006/05/20/vmware-io-problems

and for some "official" treatment of the topic, this

http://www.vmware.com/pdf/esx3_partition_align.pdf

and a couple of whitepapers from HP on the same subject:

http://forums1.itrc.hp.com/service/...56062&admit=-682735245+1171130599425+28353475

I also have a Powerpoint from an EMC presentation on the same subject at
VMWorld 2005, which outlines the same issues and solutions (and points
out a flaw in DiskparT.exe as well, thus they recommend using Diskpar)

Actually, I agree it probably isn't going to make an enormous difference
but even if nothing else, it helps control for one variable when you're
trying to isolate other I/O performance problems, especially on a RAID.

 

[rcebolleto]

I forgot to add this, by the MS Exchange team

http://msexchangeteam.com/archive/2005/08/10/408950.aspx

 

[Arno Wagner]

I forgot to add this, by the MS Exchange team

http://msexchangeteam.com/archive/2005/08/10/408950.aspx

Hmmm. Interesting.

This should not be happening. But apparently some systems are still
stuck in the dark ages and need this black-magic type optimizations to
perform well.

Ok, then. I take my statement back.

Arno

 

[Folkert Rienstra]

Hmmm. Interesting.

That you were clueless again? No, not really.

This should not be happening. But apparently some systems are still
stuck in the dark ages and need this black-magic type optimizations to
perform well.

Ok, then. I take my statement back.

What statement. There was a statement?
Wasn't it just your usual rambling: "I have no clue but ramble anyway"?