Re: 4k sector drives

Re: 4k sector drives

[Khelben Blackstaff]

> What MAY hurt, also for large writes, are the meta-data operations while 
> writing the file. (e.g. the file-size changes, journaling ...)

> But i haven't tested that and can't say for sure how much that hurts.

It hurts a lot. On my 1TB EARS when i was benchmarking unaligned
partitions, untarring a linux kernel for example took ages. (tar output
finished quickly but then you had to wait a long time till the shell
prompt returns)

With aligned partition, performance is normal.



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Re: 4k sector drives

[Emmanuel Florac]

Le Fri, 23 Jul 2010 18:02:11 +0300
Khelben Blackstaff <eye.of.the.8eholder@gmail.com> écrivait:

> It hurts a lot. On my 1TB EARS when i was benchmarking unaligned
> partitions, untarring a linux kernel for example took ages. (tar
> output finished quickly but then you had to wait a long time till the
> shell prompt returns)

Extracting a linux tarball creates lots of very small files, so it is
expected to perform very badly on unaligned partitions. But I suppose
that copying the tarball itself to the disk could be only slightly
slower than normal.

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Re: 4k sector drives

[Christoph Hellwig]

On Sun, Jul 25, 2010 at 12:35:21AM +0200, Michael Monnerie wrote:
> Thank you Christoph for clarification, also thanks to Eric - I've been 
> aligning all partitions to a multiple of 512 sectors since a long time, 
> which fits all stripe set sizes up to 256k. Too bad that even Linux 
> fdisk and parted

Current fdisk, and with some limitations parted do the right thing
and align partitions on at least a 1MB boundary.  parted unfortunately
lowers alignment again when any kind of optimal I/O size hint is set,
but I'm still hoping for that bug to get fix in a new release.

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Re: 4k sector drives

[Michael Monnerie]

[-- Attachment #1.1: Type: Text/Plain, Size: 1400 bytes --]

On Samstag, 24. Juli 2010 Eric Sandeen wrote:
> > If it really is one using -s size=4096 is the right thing to do.
> 
> Haven't read the whole thread so maybe this is redundant, but make
> sure all partitions (if any) are 4k aligned as well (unless it has
> the secret-handshake sector 63 offset...)
 
Thank you Christoph for clarification, also thanks to Eric - I've been 
aligning all partitions to a multiple of 512 sectors since a long time, 
which fits all stripe set sizes up to 256k. Too bad that even Linux 
fdisk and parted still don't do something like that, today I setup a 
Novell SLES 11 with XEN VM, and everywhere parted would align the first 
partition (when using GPT) to sector 34.. what a number.. Good that 4K 
sector drives arrive now, so the tools will hopefully change for a 
better default.

BTW: AFAIK SSD drives have a (sometimes very large) internal alignment 
of bytes which should be used as a "stripe size" to meet the optimal I/O 
size. Is there a way to find out how big that is yet?

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Re: 4k sector drives

[Eric Sandeen]

Christoph Hellwig wrote:
> On Fri, Jul 23, 2010 at 12:59:07PM +0200, Michael Monnerie wrote:
>> On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
>>> -b size=4096 is the default anyway, for 4k sector drivers you also
>>>  want -s size=4096, which you do not want for 512 byte sector disks.
>> Thanks for clarification. Should I use "-s size=4096" despite the drive 
>> saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
>> it extra for XFS helps performance? Or does it not matter at all?
> 
> If it really is one using -s size=4096 is the right thing to do.

Haven't read the whole thread so maybe this is redundant, but make
sure all partitions (if any) are 4k aligned as well (unless it has
the secret-handshake sector 63 offset...)

-Eric

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Re: 4k sector drives

[Christoph Hellwig]

On Fri, Jul 23, 2010 at 12:59:07PM +0200, Michael Monnerie wrote:
> On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
> > -b size=4096 is the default anyway, for 4k sector drivers you also
> >  want -s size=4096, which you do not want for 512 byte sector disks.
> 
> Thanks for clarification. Should I use "-s size=4096" despite the drive 
> saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
> it extra for XFS helps performance? Or does it not matter at all?

If it really is one using -s size=4096 is the right thing to do.

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Re: 4k sector drives

[Matthias Schniedermeyer]

On 23.07.2010 15:50, Emmanuel Florac wrote:
> Le Fri, 23 Jul 2010 15:38:43 +0200
> Matthias Schniedermeyer <ms@citd.de> écrivait:
> 
> > Only for writes, reads are for practically unaffected.
> 
> Sequential writes may be relatively unaffected too; if you write
> sequentially a couple of megabytes you'll have only a couple of
> additional blocks at the beginning and end of operation.

What MAY hurt, also for large writes, are the meta-data operations while 
writing the file. (e.g. the file-size changes, journaling ...)

But i haven't tested that and can't say for sure how much that hurts.




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Re: 4k sector drives

[Emmanuel Florac]

Le Fri, 23 Jul 2010 15:38:43 +0200
Matthias Schniedermeyer <ms@citd.de> écrivait:

> Only for writes, reads are for practically unaffected.

Sequential writes may be relatively unaffected too; if you write
sequentially a couple of megabytes you'll have only a couple of
additional blocks at the beginning and end of operation.

However random  and small IOs should be seriously hit.

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Re: 4k sector drives

[Matthias Schniedermeyer]

On 23.07.2010 08:10, Stan Hoeppner wrote:
> Michael Monnerie put forth on 7/23/2010 5:59 AM:
> > On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
> >> -b size=4096 is the default anyway, for 4k sector drivers you also
> >>  want -s size=4096, which you do not want for 512 byte sector disks.
> > 
> > Thanks for clarification. Should I use "-s size=4096" despite the drive 
> > saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
> > it extra for XFS helps performance? Or does it not matter at all?
> >  
> >> What values do the files
> >>
> >>         /sys/block/<device>/queue/logical_block_size
> >>         /sys/block/<device>/queue/physical_block_size
> >>         /sys/block/<device>/alignment_offset
> >>
> >> say about your disk?
> > 
> > 512, 512, 0 for a Western Digital D20EARS-00MVWB0 (2TB) which has 4K 
> > sectors but obviously hides it.
> 
> The WD20EARS-00MVWB0 is definitely a 4k sector drive:
> http://products.wdc.com/Library/Flyer/ENG/2178-771123.pdf
> 
> If you're currently seeing somewhere between 60-120MB/s per drive with hdparm
> or dd then you don't need to further tweak anything.  If alignment is off,
> from all I've read, performance will be abysmal, down in the sub 30MB/s range.

Only for writes, reads are for practically unaffected.

The problem for write is the "Read Modify Write" Cycle that is needed 
when you don't change all 8 512byte "sub-"sectors contained in a 4096 
byte sector.





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Re: 4k sector drives

[Stan Hoeppner]

Michael Monnerie put forth on 7/23/2010 5:59 AM:
> On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
>> -b size=4096 is the default anyway, for 4k sector drivers you also
>>  want -s size=4096, which you do not want for 512 byte sector disks.
> 
> Thanks for clarification. Should I use "-s size=4096" despite the drive 
> saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
> it extra for XFS helps performance? Or does it not matter at all?
>  
>> What values do the files
>>
>>         /sys/block/<device>/queue/logical_block_size
>>         /sys/block/<device>/queue/physical_block_size
>>         /sys/block/<device>/alignment_offset
>>
>> say about your disk?
> 
> 512, 512, 0 for a Western Digital D20EARS-00MVWB0 (2TB) which has 4K 
> sectors but obviously hides it.

The WD20EARS-00MVWB0 is definitely a 4k sector drive:
http://products.wdc.com/Library/Flyer/ENG/2178-771123.pdf

If you're currently seeing somewhere between 60-120MB/s per drive with hdparm
or dd then you don't need to further tweak anything.  If alignment is off,
from all I've read, performance will be abysmal, down in the sub 30MB/s range.

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Re: 4k sector drives

[Emmanuel Florac]

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Le Fri, 23 Jul 2010 12:59:07 +0200
Michael Monnerie <michael.monnerie@is.it-management.at> écrivait:

> Thanks for clarification. Should I use "-s size=4096" despite the
> drive saying 512b sectors? It's a "hidden" 4K sector drive, so maybe
> declaring it extra for XFS helps performance? Or does it not matter
> at all?

I'd say it's the right time for a benchmark :)

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Re: 4k sector drives

[Stan Hoeppner]

Christoph Hellwig put forth on 7/23/2010 5:47 AM:
> On Fri, Jul 23, 2010 at 05:42:59AM -0500, Stan Hoeppner wrote:
>> FWIW, for comparison, my 500GB Blue series WD5000AAKS-00V1A0 shows
>>
>> logical_block_size	512
>> physical_block_size	512
>> alignment_offset	0
> 
> Which means there is absolutely no visible 4k sector support.

Sorry for the confusion Christoph.

I meant for comparison to a plain old 512 byte/sec drive from the same
manufacturer.  The Western Digital Caviar Blue model WD5000AAKS, my drive
above, has 512 byte sectors.  His 2TB Caviar Green has 4096 byte sectors.

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Re: 4k sector drives

[Michael Monnerie]

[-- Attachment #1.1: Type: Text/Plain, Size: 1107 bytes --]

On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
> -b size=4096 is the default anyway, for 4k sector drivers you also
>  want -s size=4096, which you do not want for 512 byte sector disks.

Thanks for clarification. Should I use "-s size=4096" despite the drive 
saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
it extra for XFS helps performance? Or does it not matter at all?
 
> What values do the files
> 
>         /sys/block/<device>/queue/logical_block_size
>         /sys/block/<device>/queue/physical_block_size
>         /sys/block/<device>/alignment_offset
> 
> say about your disk?

512, 512, 0 for a Western Digital D20EARS-00MVWB0 (2TB) which has 4K 
sectors but obviously hides it.

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Re: 4k sector drives

[Christoph Hellwig]

On Fri, Jul 23, 2010 at 05:42:59AM -0500, Stan Hoeppner wrote:
> FWIW, for comparison, my 500GB Blue series WD5000AAKS-00V1A0 shows
> 
> logical_block_size	512
> physical_block_size	512
> alignment_offset	0

Which means there is absolutely no visible 4k sector support.

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Re: 4k sector drives

[Stan Hoeppner]

Christoph Hellwig put forth on 7/23/2010 4:58 AM:

> What values do the files
> 
> 	/sys/block/<device>/queue/logical_block_size
> 	/sys/block/<device>/queue/physical_block_size
> 	/sys/block/<device>/alignment_offset
> 
> say about your disk?

FWIW, for comparison, my 500GB Blue series WD5000AAKS-00V1A0 shows

logical_block_size	512
physical_block_size	512
alignment_offset	0

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Re: 4k sector drives

[Christoph Hellwig]

On Fri, Jul 23, 2010 at 08:09:27AM +0200, Michael Monnerie wrote:
> On Mittwoch, 21. Juli 2010 Khelben Blackstaff wrote:
> > Nevertheless, you don't have to get them to report 4k to linux. As
> >  long as you align the partitions its fine. As i said in the other
> >  post, newer fdisk doesn't use "DOS compatibility mode" and uses
> >  sectors by default (instead of stupid CHS) with a 1MB alignment, so
> >  every partition will be properly aligned. If you don't dual boot
> >  Windows, you can also use GPT partitioning scheme. Also, from what i
> >  have seen, xfsprogs are quite clever and find most stuff on their
> >  own. I usually mkfs with "-s size=4096" just to be sure.
> 
> I always do -b size=4096 anyway, so I'm fine here. And I created the 
> partitions starting sector 512, so that should be good also.

-b size=4096 is the default anyway, for 4k sector drivers you also want
-s size=4096, which you do not want for 512 byte sector disks.

What values do the files

	/sys/block/<device>/queue/logical_block_size
	/sys/block/<device>/queue/physical_block_size
	/sys/block/<device>/alignment_offset

say about your disk?


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Re: 4k sector drives

[Khelben Blackstaff]

> Thanks, I did this, and it even worked for my other WDC 
> WD2002FYPS-01U1B0, which was on 12 seconds (the EARS were on 8s as you 
> said), and now all three drives have a 120s delay before parking. That 

I am glad it worked.

>should be sufficient. It didn't work for the VelociRaptor in my PC, just 
> to mention.

Disks from the Green series support some features that help the
enviroment. Among them is having lower rpm (usually 5400) and
the intellipark feature that you set to 120s.

If i am not mistaken, VelociRaptor is the low latency 10K rpm
drive, so it's not surprising that it doesn't support this. Only
drives from the Green series do.

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Re: 4k sector drives

[Michael Monnerie]

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On Mittwoch, 21. Juli 2010 Khelben Blackstaff wrote:
> Nevertheless, you don't have to get them to report 4k to linux. As
>  long as you align the partitions its fine. As i said in the other
>  post, newer fdisk doesn't use "DOS compatibility mode" and uses
>  sectors by default (instead of stupid CHS) with a 1MB alignment, so
>  every partition will be properly aligned. If you don't dual boot
>  Windows, you can also use GPT partitioning scheme. Also, from what i
>  have seen, xfsprogs are quite clever and find most stuff on their
>  own. I usually mkfs with "-s size=4096" just to be sure.

I always do -b size=4096 anyway, so I'm fine here. And I created the 
partitions starting sector 512, so that should be good also.

> Slightly offtopic, there is another "problem" with these drives. They
>  park the heads every 8 seconds, so they might wear prematurely. You
>  can change the 8sec timer or disable it with the wdidle3 utility
>  from this url
> http://support.wdc.com/product/download.asp?groupid=609&sid=113&a
> mp;lang=en
> 
> If you want to know more about the problem, there are many forums
>  where you can read about wdidle3 and i also posted about it on my
>  blog.
>  http://lordkhelben.wordpress.com/2010/05/15/wd-caviar-green-hard-dis
> ks-idle-settings/
 
Thanks, I did this, and it even worked for my other WDC 
WD2002FYPS-01U1B0, which was on 12 seconds (the EARS were on 8s as you 
said), and now all three drives have a 120s delay before parking. That 
should be sufficient. It didn't work for the VelociRaptor in my PC, just 
to mention.

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Re: 4k sector drives

[Michael Monnerie]

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On Mittwoch, 21. Juli 2010 Khelben Blackstaff wrote:
> I hope i helped.
 
Sound good, will try and report back. Thx.

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Re: 4k sector drives

[Emmanuel Florac]

[-- Attachment #1.1: Type: text/plain, Size: 996 bytes --]

Le Wed, 21 Jul 2010 11:14:15 +0200
Michael Monnerie <michael.monnerie@is.it-management.at> écrivait:

> I have these:
> Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20035646
> Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20028252
> 
> Any chance to get Linux know they are 4k sector drives manually?

From what I've read here and there, apparently they'll always present
512 bytes blocks, bu the system is somehow aware that the underlying
block is 4K large, apparently. It isn't very clear... 

BTW, I suppose that with such a drive, it's highly commendable to use
4K FS blocks (or larger) instead of the common 1K ones...

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Re: 4k sector drives

[Khelben Blackstaff]

> I have these:
> Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20035646
> Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20028252

> Any chance to get Linux know they are 4k sector drives manually?

Your revision numbers are different than mine, because you have the 2TB drive,
but i guess its the same for these too. You can try "hdparm -I /dev/sdX" (capital i)
or "cat /sys/block/sdX/queue/hw_sector_size" to see what they report.

Mine report "Logical/Physical Sector size:           512 bytes"
There are newer revisions that report "Physical Sector size: 4096 bytes"

Nevertheless, you don't have to get them to report 4k to linux. As long as you
align the partitions its fine. As i said in the other post, newer fdisk doesn't use
"DOS compatibility mode" and uses sectors by default (instead of stupid CHS)
with a 1MB alignment, so every partition will be properly aligned. If you don't
dual boot Windows, you can also use GPT partitioning scheme.
Also, from what i have seen, xfsprogs are quite clever and find most stuff on
their own. I usually mkfs with "-s size=4096" just to be sure.

Slightly offtopic, there is another "problem" with these drives. They park the heads
every 8 seconds, so they _might_ wear prematurely. You can change the 8sec timer
or disable it with the wdidle3 utility from this url
http://support.wdc.com/product/download.asp?groupid=609&sid=113&lang=en

If you want to know more about the problem, there are many forums where
you can read about wdidle3 and i also posted about it on my blog.
http://lordkhelben.wordpress.com/2010/05/15/wd-caviar-green-hard-disks-idle-settings/

I hope i helped.

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Re: 4k sector drives

[Michael Monnerie]

[-- Attachment #1.1: Type: Text/Plain, Size: 975 bytes --]

On Mittwoch, 21. Juli 2010 Khelben Blackstaff wrote:
> No, don't set the jumper.

OK, luckily I didn't have time until now :-)

> WD EARS drives with 00Y model revision doesn't report the sector size
> properly and only report 512 bytes. (Use hdparm to see it)
> Those with 00Z revision report correctly that they have 4096 physical
> sector size and 512 logical sector size.

I have these:
Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20035646
Model=WDC WD20EARS-00MVWB0, FwRev=50.0AB50, SerialNo=WD-WMAZ20028252

Any chance to get Linux know they are 4k sector drives manually?

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RE: 4k sector drives

[Khelben Blackstaff]

> shows a jumper exists for "advanced format", but doesn't tell what it 
> does. I'll try to set or unset it depending on what it is now, and see 
> if there's a difference.

No, don't set the jumper.

Because DOS required the first head to be empty for some reason
and because allmost every geometry uses 63 sectors per track,
the first partition usually starts at sector 63. The jumper tells the
disk firmware to use a mapping so that the sectors fall in a 4096
boundary. (It uses either +1 or -7 offset). So, the OS thinks it writes
to sector 63 while it truly writes to sector 64 (or 56). Every sector
is transparently mapped using this offset.

This jumper exists to be used only with legacy OSes like Windows XP
and makes sense when there is only one primary partition which covers
the whole disk.

So, don't use the jumper in linux but align properly the partitions.
fdisk from util-linux-ng > 0.17 align on 1MB so everything will be fine.
If you use an older version then align the partitions manually.

WD EARS drives with 00Y model revision doesn't report the sector size
properly and only report 512 bytes. (Use hdparm to see it)
Those with 00Z revision report correctly that they have 4096 physical
sector size and 512 logical sector size.

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Re: 4k sector drives

[Michael Monnerie]

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On Dienstag, 20. Juli 2010 Emmanuel Florac wrote:
> They come in emulation mode (like many SATA-II drives came in SATA-I
> mode). You must set them to 4K blocks manually, for WD IIRC with a
>  DOS software. And you need a controller that supports 4K blocks, too
>  (probably anything older than a year won't).
 
Thank you Emmanuel and Stan,

http://wdc-de.custhelp.com/cgi-
bin/wdc_de.cfg/php/enduser/std_adp.php?p_faqid=5324&p_created=&p_cats=185&p_cv=1.185&p_pv=2.294&p_prods=227%2C294#jumper

shows a jumper exists for "advanced format", but doesn't tell what it 
does. I'll try to set or unset it depending on what it is now, and see 
if there's a difference.

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Re: 4k sector drives

[Emmanuel Florac]

Le Tue, 20 Jul 2010 20:58:27 +0200 vous écriviez:

> I recently bought 2 new 4k sector drives (WD Caviar Green 2TB, 
> WD20EARS), but Linux kernel 2.6.34.1 still says:
> 
> # blockdev --getss /dev/sdd
> 512
> 
> Shouldn't that be 4096? Where is the problem?

They come in emulation mode (like many SATA-II drives came in SATA-I
mode). You must set them to 4K blocks manually, for WD IIRC with a DOS
software. And you need a controller that supports 4K blocks, too
(probably anything older than a year won't).

-- 
------------------------------------------------------------------------
Emmanuel Florac     |   Direction technique
                    |   Intellique
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                    |   +33 1 78 94 84 02
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Re: 4k sector drives

[Stan Hoeppner]

Michael Monnerie put forth on 7/20/2010 1:58 PM:
> Dear list, I don't know who else to ask this:
> 
> I recently bought 2 new 4k sector drives (WD Caviar Green 2TB, 
> WD20EARS), but Linux kernel 2.6.34.1 still says:
> 
> # blockdev --getss /dev/sdd
> 512
> 
> Shouldn't that be 4096? Where is the problem?

Firmware sector size translation is the problem.  The WD20EARS is apparently
not a native 4096K sector size drive, but a transitional product.  It is 4k
sector size internally but the firmware translates this to 512B sectors to the
OS driver.  It's a hybrid.

Google "WD20EARS sector size"

-- 
Stan

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4k sector drives

[Michael Monnerie]

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Dear list, I don't know who else to ask this:

I recently bought 2 new 4k sector drives (WD Caviar Green 2TB, 
WD20EARS), but Linux kernel 2.6.34.1 still says:

# blockdev --getss /dev/sdd
512

Shouldn't that be 4096? Where is the problem?


-- 
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services
http://proteger.at [gesprochen: Prot-e-schee]
Tel: 0660 / 415 65 31

****** Aktuelles Radiointerview! ******
http://www.it-podcast.at/aktuelle-sendung.html

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