Is there any relationship between Sector Size and File Allocation Unit ?

[Guest Peter]

Hi,

 

For SQL Server, a fellow has suggested to use File Allocation Unit of size

64KB and the sector size should be 4KB.

 

I am able to format a new hard disk and assign a file allocation unit size

of 64KB. On the other hand, is there any way for us to change the sector

size and what is the default value for a Windows 2003 Server ?

 

Thanks

Peter

[Guest Dave Patrick]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

I think you must buy them this way.

 

http://www.microsoft.com/communities/newsgroups/en-us/default.aspx?dg=microsoft.public.sqlserver.server&tid=fe3a5d7e-61a4-4934-ab59-d02bce120518&p=1

 

http://support.microsoft.com/kb/926930

 

http://support.microsoft.com/kb/923332

 

http://www.techworld.com/storage/news/index.cfm?newsid=5653

 

 

--

 

Regards,

 

Dave Patrick ....Please no email replies - reply in newsgroup.

Microsoft Certified Professional

Microsoft MVP [Windows]

http://www.microsoft.com/protect

 

"Peter" wrote:

> Hi,

>

> For SQL Server, a fellow has suggested to use File Allocation Unit of size

> 64KB and the sector size should be 4KB.

>

> I am able to format a new hard disk and assign a file allocation unit size

> of 64KB. On the other hand, is there any way for us to change the sector

> size and what is the default value for a Windows 2003 Server ?

>

> Thanks

> Peter

>

>

[Guest Dave Patrick]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Yes.

 

--

 

Regards,

 

Dave Patrick ....Please no email replies - reply in newsgroup.

Microsoft Certified Professional

Microsoft MVP [Windows]

http://www.microsoft.com/protect

 

"Peter" wrote:

> Dear Dave,

>

> Thank you for your advice. From the URL, my understanding is that the

> sector size is 512 Byte that is determined by the HD manufacturer. Is my

> understanding correct ?

>

> Thanks

> Peter

[Guest Peter]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Dear Dave,

 

Thank you for your advice. From the URL, my understanding is that the

sector size is 512 Byte that is determined by the HD manufacturer. Is my

understanding correct ?

 

Thanks

Peter

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:719AB9D2-80B1-4635-9865-66840D75B1D5@microsoft.com...

>I think you must buy them this way.

>

> http://www.microsoft.com/communities/newsgroups/en-us/default.aspx?dg=microsoft.public.sqlserver.server&tid=fe3a5d7e-61a4-4934-ab59-d02bce120518&p=1

>

> http://support.microsoft.com/kb/926930

>

> http://support.microsoft.com/kb/923332

>

> http://www.techworld.com/storage/news/index.cfm?newsid=5653

>

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "Peter" wrote:

>> Hi,

>>

>> For SQL Server, a fellow has suggested to use File Allocation Unit of

>> size 64KB and the sector size should be 4KB.

>>

>> I am able to format a new hard disk and assign a file allocation unit

>> size of 64KB. On the other hand, is there any way for us to change the

>> sector size and what is the default value for a Windows 2003 Server ?

>>

>> Thanks

>> Peter

>>

>>

>

[Guest Peter]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Dear Dave,

 

Thank you for your advice. It is much appreciated.

 

Peter

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:A8213628-80B5-4656-84D5-9DE5EB3C1B6C@microsoft.com...

> Yes.

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "Peter" wrote:

>> Dear Dave,

>>

>> Thank you for your advice. From the URL, my understanding is that the

>> sector size is 512 Byte that is determined by the HD manufacturer. Is my

>> understanding correct ?

>>

>> Thanks

>> Peter

>

[Guest Peter]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Dear Dave,

 

Another fellow suggests that the stripe size of the SAN should also be 64KB

before using allocation size of 64KB.

 

As there may be more than 1 LUN is created for that RAID Group, would it be

a problem if other LUN are used by file server / web server ?

 

Thanking you in anticipation.

 

Peter

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:719AB9D2-80B1-4635-9865-66840D75B1D5@microsoft.com...

>I think you must buy them this way.

>

> http://www.microsoft.com/communities/newsgroups/en-us/default.aspx?dg=microsoft.public.sqlserver.server&tid=fe3a5d7e-61a4-4934-ab59-d02bce120518&p=1

>

> http://support.microsoft.com/kb/926930

>

> http://support.microsoft.com/kb/923332

>

> http://www.techworld.com/storage/news/index.cfm?newsid=5653

>

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "Peter" wrote:

>> Hi,

>>

>> For SQL Server, a fellow has suggested to use File Allocation Unit of

>> size 64KB and the sector size should be 4KB.

>>

>> I am able to format a new hard disk and assign a file allocation unit

>> size of 64KB. On the other hand, is there any way for us to change the

>> sector size and what is the default value for a Windows 2003 Server ?

>>

>> Thanks

>> Peter

>>

>>

>

[Guest Dave Patrick]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Let's ask them here. x-posted to:microsoft.public.storage

 

 

--

 

Regards,

 

Dave Patrick ....Please no email replies - reply in newsgroup.

Microsoft Certified Professional

Microsoft MVP [Windows]

http://www.microsoft.com/protect

 

"Peter" wrote:

> Dear Dave,

>

> Another fellow suggests that the stripe size of the SAN should also be

> 64KB before using allocation size of 64KB.

>

> As there may be more than 1 LUN is created for that RAID Group, would it

> be a problem if other LUN are used by file server / web server ?

>

> Thanking you in anticipation.

>

> Peter

[Guest John Fullbright]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

A sector is generally 512 bytes. An allocation unit or cluster is composed

of sectors, so it's size would be a multiple of the sector size. In NTFS,

the default allocation unit or cluster size is 4K; that's 16 sectors.

 

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:047038D2-C6F1-4D7B-B544-ECD575A7F1C8@microsoft.com...

> Let's ask them here. x-posted to:microsoft.public.storage

>

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "Peter" wrote:

>> Dear Dave,

>>

>> Another fellow suggests that the stripe size of the SAN should also be

>> 64KB before using allocation size of 64KB.

>>

>> As there may be more than 1 LUN is created for that RAID Group, would it

>> be a problem if other LUN are used by file server / web server ?

>>

>> Thanking you in anticipation.

>>

>> Peter

>

[Guest Dave Patrick]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

The op wants to change the sector size.

 

--

 

Regards,

 

Dave Patrick ....Please no email replies - reply in newsgroup.

Microsoft Certified Professional

Microsoft MVP [Windows]

http://www.microsoft.com/protect

 

"John Fullbright" wrote:

>A sector is generally 512 bytes. An allocation unit or cluster is composed

>of sectors, so it's size would be a multiple of the sector size. In NTFS,

>the default allocation unit or cluster size is 4K; that's 16 sectors.

[Guest Peter]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Dear Dave,

 

From my understanding, even though we choose "File Allocation Unit" to 64KB,

the sector is still 512 byte. Is it correct ?

 

Thanks

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:430D613C-44B4-4C9D-A987-C1CB74EC8765@microsoft.com...

> The op wants to change the sector size.

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "John Fullbright" wrote:

>>A sector is generally 512 bytes. An allocation unit or cluster is

>>composed of sectors, so it's size would be a multiple of the sector size.

>>In NTFS, the default allocation unit or cluster size is 4K; that's 16

>>sectors.

>

[Guest John Fullbright]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Today, the industry standard is a 512 byte sector. If you could somehow

muck with that, you would be setting yourself up for major issues.

 

In the future, disk manufacturarers will begin producing disks with larger

sectors. Windows Vista is the only MS OS I know of that is set to support

this, although longhorn would be likely. The method used to support this is

generally emulation; where the internal sector size is larger than 512 bytes

but the disk exposes a logical sector size of 512 bytes. The biggest

obsticle to larger sector sizes is backwards compatibility, and emulation is

one way around it.

 

If ops whats to change something, it's most likely the allocation unit or

cluster size. This is a grouping of sectors and is set at the time the disk

is formatted. Changing the cluster size is a destructive process; you'll

need to back up the disk first and restore the data after you're done.

 

 

"Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

news:430D613C-44B4-4C9D-A987-C1CB74EC8765@microsoft.com...

> The op wants to change the sector size.

>

> --

>

> Regards,

>

> Dave Patrick ....Please no email replies - reply in newsgroup.

> Microsoft Certified Professional

> Microsoft MVP [Windows]

> http://www.microsoft.com/protect

>

> "John Fullbright" wrote:

>>A sector is generally 512 bytes. An allocation unit or cluster is

>>composed of sectors, so it's size would be a multiple of the sector size.

>>In NTFS, the default allocation unit or cluster size is 4K; that's 16

>>sectors.

>

[Guest Dave Patrick]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Yes, this is correct.

 

--

 

Regards,

 

Dave Patrick ....Please no email replies - reply in newsgroup.

Microsoft Certified Professional

Microsoft MVP [Windows]

http://www.microsoft.com/protect

 

"Peter" wrote:

> Dear Dave,

>

> From my understanding, even though we choose "File Allocation Unit" to

> 64KB, the sector is still 512 byte. Is it correct ?

>

> Thanks

[Guest Kenny Speer]

Re: Is there any relationship between Sector Size and File Allocation Unit ?

 

Actually, the key word here is *support*. Windows 2003 and later will

detect and use a disk with a >512byte sector size without issue. Microsoft

does not outright claim they don't support this, it's just very unlikely to

see it. Now, there is at least one storage vendor which exports the disk

sector size of 1k (I know cause I helped build that product a few years

ago). Windows 2003 had no issue using the disk. In fact, the max size of a

LUN for 2003 is 2TB and this is a limit imposed by 2^32 sectors * 512B, but

with 1K sectors, this max size is 4TB. Microsoft cannot limit the sector

size, since other media uses 2k, 4k,8k sectors (tape, cdrom, etc).

 

This isn't common, and you, AFAIK, cannot change the sector size on the

storage device. And you probably wouldn't want to. The NTFS allocation

size simply must be a multiple of the sector size (i.e. cannot write to the

middle of the sector).

 

The original OP question actually had nothing to do with the sector size but

RAID stripe size and alignment. Was that question answered?

 

~kenny

 

"John Fullbright" <fjohn@donotspamnetappdotcom> wrote in message

news:%23M1ECy2CIHA.4472@TK2MSFTNGP05.phx.gbl...

> Today, the industry standard is a 512 byte sector. If you could somehow

> muck with that, you would be setting yourself up for major issues.

>

> In the future, disk manufacturarers will begin producing disks with larger

> sectors. Windows Vista is the only MS OS I know of that is set to support

> this, although longhorn would be likely. The method used to support this

> is generally emulation; where the internal sector size is larger than 512

> bytes but the disk exposes a logical sector size of 512 bytes. The

> biggest obsticle to larger sector sizes is backwards compatibility, and

> emulation is one way around it.

>

> If ops whats to change something, it's most likely the allocation unit or

> cluster size. This is a grouping of sectors and is set at the time the

> disk is formatted. Changing the cluster size is a destructive process;

> you'll need to back up the disk first and restore the data after you're

> done.

>

>

> "Dave Patrick" <DSPatrick@nospam.gmail.com> wrote in message

> news:430D613C-44B4-4C9D-A987-C1CB74EC8765@microsoft.com...

>> The op wants to change the sector size.

>>

>> --

>>

>> Regards,

>>

>> Dave Patrick ....Please no email replies - reply in newsgroup.

>> Microsoft Certified Professional

>> Microsoft MVP [Windows]

>> http://www.microsoft.com/protect

>>

>> "John Fullbright" wrote:

>>>A sector is generally 512 bytes. An allocation unit or cluster is

>>>composed of sectors, so it's size would be a multiple of the sector size.

>>>In NTFS, the default allocation unit or cluster size is 4K; that's 16

>>>sectors.

>>

>

>