RE: [t13] FW: 48-bit address implications on partition table

[Mcgrath, Jim]

Title: RE: [t13] FW: 48-bit address implications on partition table

 

Note that 2 TB is not too far off.  At a doubling of density every year (which could slow down of course), a single HDD will have this in a bit more than 3 years.  Worse, if you have a RAID with two drives the time is 2 years off - with 4 drives less than 1 year.

 

Considering how long it takes software to be developed and rolled out to the industry, that's not a very long time.

 

Jim

 

So the 32 bit limitation applies to LBA, not just clusters, at least at the class driver interface layer?

 

 

-----Original Message-----
From: Eschmann, Michael K [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, February 13, 2002 8:02 AM
To: Mcgrath, Jim; 'Curtis Stevens'; 't13'
Subject: RE: [t13] FW: 48-bit address implications on partition table

Jim,

 

NTFS may be able to handle 64-bit LBA's, but the class layer beneath them can only handle 32bit LBA's. 

 

The SRB structure defined in the Windows DDK only has a 34-bit LBA field.  Microsoft is quite aware of the issue and I believe plans on upgrading to a bigger LBA field in the SRB (or some fix like it) in future OS's.  As for time, we have until we get to 2TB to get it worked out.

 

Regards, MKE.

 

 

-----Original Message-----
From: Mcgrath, Jim [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 12, 2002 11:07 AM
To: 'Curtis Stevens'; 't13'
Subject: RE: [t13] FW: 48-bit address implications on partition table

 

48 bit addressing at the ATA level does nothing to affect the way partitions are used.  If a partition only allows for 32 bit LBAs (e.g. Fat-32), then only that size LBA can be passed via the file system to the ATA device.  So while the ATA device requires 48 bit ATA addressing, only 32 of those bits can be non zero in this case.

 

This is exactly the same as using a partition that restricts LBAs to 16 bits (e.g. FAT-16) with the original ATA LBA addressing.  Although the ATA interface allows the use of 28 bits in the LBA, only 16 could be non zero.

 

Notice that partitions issues are NOT standardized by the ATA standard, but instead are file system unique.

 

Jim

 

PS there are actually file systems today that can take full advantage of the 48 bit addressing, since they can have 64 bit LBAs.  But they are just now getting into common use (I believe NTFS is one).

-----Original Message-----
From: Curtis Stevens [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 12, 2002 9:50 AM
To: 't13'
Subject: RE: [t13] FW: 48-bit address implications on partition table

I think the current limit is about 2TB given a 512 byte sector.  Larger sector sizes would of course push the limit higher.  I know that we now commonly see RAID running in the 1TB-10TB range.  Depending on the nature of the solution for these boxes, the problem may have already been solved.

-----------------------
Curtis E. Stevens
Pacific Digital Corp.
2052 Alton Parkway
Irvine, CA 92606

Phone (949) 477-5713
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WEB: www.PacificDigital.com

The face of a child can say it all, especially the mouth part of the face...

-----Original Message-----
From: Mclean, Pete [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 12, 2002 7:17 AM
To: 't13'
Subject: [t13] FW: 48-bit address implications on partition table

This message is from the T13 list server.

Can someone answer this one?

-----Original Message-----
From: sraposo [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 12, 2002 9:11 AM
To: [EMAIL PROTECTED]
Subject: 48-bit address implications on partition table

Dear Mr. Mclean,

I have a forensics-related business and I would like to know if there
already is some defined standard about a partition table that handles
partition initial LBA address on 48-bit format, since the tradition
partition table handles only 32-bit adresses. ATA-6 is already available and
I guess that there must be some HDD manufacturer about to lauch some model
over 137GB. So, it is a kind of urgent matter.

I very thank you for any help.

Sincerily,
........................................................................
Perito S�rgio Raposo - Niter�i - RJ (Brazil)
........................................................................

(see english version of this signature below)

Resgate cient�fico de arquivos, per�cia investigativa de dados,
quebra �tica de prote��o e desenvolvimento de software b�sico.

   http://www.recuperacaodedados.com.br
   http://www.periciadigital.com.br

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