LCN and physical sector

NTFSD
1

Hi all,

just two questions…

  1. How can I find out the cluster size of a volume (f.e “C:”) used by
    FAT or NTFS from a kernel mode driver? (Any other possibility than
    reading the boot record and interpreting its content.)

  2. Is there a way to convert the LCN of a file to the physical sector
    number of the harddisk ?

Thanks,

Gerhard Wallhäußer

2

> 1. How can I find out the cluster size of a volume (f.e “C:”) used
by

FAT or NTFS from a kernel mode driver? (Any other possibility than
reading the boot record and interpreting its content.)

Send the query volume information IRP. The details are in NTIFS.H

  1. Is there a way to convert the LCN of a file to the physical
    sector
    number of the harddisk ?

FSCTL_QUERY_RETRIEVAL_POINTERS will return the runlist for a file.

Max

3

Maxim S. Shatskih wrote:

>1. How can I find out the cluster size of a volume (f.e “C:”) used

by

>FAT or NTFS from a kernel mode driver? (Any other possibility than
>reading the boot record and interpreting its content.)

Send the query volume information IRP. The details are in NTIFS.H

Ok.

>2. Is there a way to convert the LCN of a file to the physical

sector

>number of the harddisk ?

FSCTL_QUERY_RETRIEVAL_POINTERS will return the runlist for a file.

Max

Ok, but in ntifs.h I can find the following comment:

// Note: FSCTL_QUERY_RETRIEVAL_POINTER and FSCTL_MARK_AS_SYSTEM_HIVE only
// work from Kernel mode on local paging files or the system hives.

So it seems that FSCTL_QUERY_RETRIEVAL_POINTER can not be used on usual
files?

If it will work on usual files, what are the structures used with
FSCTL_QUERY_RETRIEVAL_POINTERS?

BTW:

What are the differences between FSCTL_QUERY_RETRIEVAL_POINTERS and
FSCTL_GET_RETRIEVAL_POINTERS?

Thanks,
Gerhard

4

Maxim S. Shatskih wrote:

>What are the differences between FSCTL_QUERY_RETRIEVAL_POINTERS and
>FSCTL_GET_RETRIEVAL_POINTERS?

Sorry. FSCTL_GET_RETRIEVAL_POINTERS for sure.
FSCTL_QUERY_RETRIEVAL_POINTERS is really for a pagefile only.

Max

FSCTL_GET_RETRIEVAL_POINTERS returns for my understanding the LCNs
(logical cluster numbers) of a file, counted from the beginning of a
volume (which means usually a partition). How can this LCN be converted
to the physical sector number of the harddisk on which the volume is
located?

Thanks,
Gerhard

5

> volume (which means usually a partition). How can this LCN be
converted

to the physical sector number of the harddisk on which the volume is
located?

IOCTL_DISK_GET_DRIVE_LAYOUT will give you the partition table of the
disk.
You will also need the mount manager IOCTLs to determine what
partition on the disk is your FS volume.

Max

6

The problem is that you assume a one-to-one mapping from the logical blocks
on a volume to the underlying physical storage - no such restriction is in
place. For example, suppose you are running a stripe set (using dynamic or
basic disks).

That is why FSCTL_QUERY_RETRIEVAL_POINTERS only works on the boot drive’s
paging file (the dump driver needs the blocks to dump it.)

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

Looking forward to seeing you at our revised and updated file systems class
in February 2003 (Boston, MA).

-----Original Message-----
From: Gerhard Wallh?u?er [mailto:gerhard.wallhaeusser@ce-infosys.com]
Sent: Tuesday, February 11, 2003 9:59 AM
To: File Systems Developers
Subject: [ntfsd] Re: LCN and physical sector

Maxim S. Shatskih wrote:

>What are the differences between FSCTL_QUERY_RETRIEVAL_POINTERS and
>FSCTL_GET_RETRIEVAL_POINTERS?

Sorry. FSCTL_GET_RETRIEVAL_POINTERS for sure.
FSCTL_QUERY_RETRIEVAL_POINTERS is really for a pagefile only.

Max

FSCTL_GET_RETRIEVAL_POINTERS returns for my understanding the LCNs
(logical cluster numbers) of a file, counted from the beginning of a
volume (which means usually a partition). How can this LCN be converted
to the physical sector number of the harddisk on which the volume is
located?

Thanks,
Gerhard

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