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WD AV drives not for desktop use



 
 
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  #1  
Old June 27th 11, 06:59 AM posted to comp.sys.ibm.pc.hardware.storage
Ed Light
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Default WD AV drives not for desktop use

http://www.techarp.com/showarticle.a...tno=659&pgno=4
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  #2  
Old June 28th 11, 05:50 PM posted to comp.sys.ibm.pc.hardware.storage
Arno[_3_]
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Default WD AV drives not for desktop use

Ed Light wrote:
http://www.techarp.com/showarticle.a...tno=659&pgno=4


Fortunately these should be more expensive and not
show up in cheap computers. But some people will
recycle them and run into problems.

Arno
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  #3  
Old June 28th 11, 07:50 PM posted to comp.sys.ibm.pc.hardware.storage
Rod Speed
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Default WD AV drives not for desktop use

Arno wrote:
Ed Light wrote:
http://www.techarp.com/showarticle.a...tno=659&pgno=4


Fortunately these should be more expensive


Not necessarily, it depends on how widespread
PVR use becomes compared with PCs etc.

and not show up in cheap computers. But some
people will recycle them and run into problems.


Thats always a potential with any recycling.


  #4  
Old June 28th 11, 07:59 PM posted to comp.sys.ibm.pc.hardware.storage
Ed Light
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Posts: 924
Default WD AV drives not for desktop use

On 6/28/2011 9:50 AM, Arno wrote:
Ed wrote:
http://www.techarp.com/showarticle.a...tno=659&pgno=4


Fortunately these should be more expensive and not
show up in cheap computers. But some people will
recycle them and run into problems.

Arno


newegg has alot of them listed. The prices are comparable to other drives.
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  #5  
Old June 28th 11, 09:14 PM posted to comp.sys.ibm.pc.hardware.storage
Arno[_3_]
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Default WD AV drives not for desktop use

Ed Light wrote:
On 6/28/2011 9:50 AM, Arno wrote:
Ed wrote:
http://www.techarp.com/showarticle.a...tno=659&pgno=4


Fortunately these should be more expensive and not
show up in cheap computers. But some people will
recycle them and run into problems.

Arno


newegg has alot of them listed. The prices are comparable to other drives.


Hmm, not good. These are not general-purpose components. If
I read it right, they do not do any error correction.

Arno
--
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GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
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  #6  
Old June 29th 11, 04:27 AM posted to comp.sys.ibm.pc.hardware.storage
Nuser
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Default WD AV drives not for desktop use

On 27/06/2011 06:59, Ed Light wrote:
http://www.techarp.com/showarticle.a...tno=659&pgno=4


A number of years ago I acquired 4x500GB Hitachi drives sold in the
sealed original packaging as part of a job lot, they were sold as
identical. However when I received the drives 2 of them were DeskStars,
1 was a faster version (which I forget the model name atm) and 1 was a
CinemaStar drive which is a similar AV-specific drive to the WD drives
mentioned in the link.

The only real difference in performance was the drive had a quicker
access times, better IO transaction rate but much slower (but *far* more
consistent) transfer rate than other drives. It is runs quieter, cooler
and sucks a little less power too (despite it still being a 7200rpm drive).

After talking to a guy who worked at Hitachi (but does no longer)he told
me that in fact these drives were *less* prone to errors when used in
normal systems, that in fact the full AV "mode" had to be enabled
specifically and the drives were shipped in a "hybrid" mode. This mode
was apparently not vendor specific so maybe the WD drives arent as bad
as this article makes out.

I wouldn't recommend them unless access time/IO rate is a priority and
definitely not if you are looking for high transfer rate, but otherwise
if you find them at a bargain price then don't shy away.



  #7  
Old June 29th 11, 07:17 PM posted to comp.sys.ibm.pc.hardware.storage
Mike Tomlinson
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Posts: 431
Default WD AV drives not for desktop use

En el artículo , Arno
escribió:

Hmm, not good. These are not general-purpose components. If
I read it right, they do not do any error correction.


Exactly. Or they do very minimal correction, favouring keeping up a
stream of data over data accuracy.

Such drives are sometimes also marked "CE" (consumer electronics), not
to be confused with the European CE symbol.

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  #8  
Old June 29th 11, 07:18 PM posted to comp.sys.ibm.pc.hardware.storage
Mike Tomlinson
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Posts: 431
Default WD AV drives not for desktop use

En el artículo , Nuser
escribió:

identical. However when I received the drives 2 of them were DeskStars,
1 was a faster version (which I forget the model name atm)


Ultrastar. IBM/Hitachi's name for their enterprise range.

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  #9  
Old June 30th 11, 09:11 AM posted to comp.sys.ibm.pc.hardware.storage
Franc Zabkar
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Posts: 1,118
Default WD AV drives not for desktop use

On Sun, 26 Jun 2011 22:59:57 -0700, Ed Light put
finger to keyboard and composed:

http://www.techarp.com/showarticle.a...tno=659&pgno=4


AFAICS, that author of that article is misinformed.

AIUI, the drive only skips over bad blocks when its Streaming Command
Set is enabled. The drive still supports the regular command set. In
fact, these commands *must* be used whenever the file system is
updated. The user of an AV-GP drive may not care about a dropped video
frame, but he must have confidence that his file system is intact.

Furthermore, a drive that supports TLER (Time Limited Error Recovery)
is to be preferred over non-TLER capable drives in RAID environments.
A drive that takes too long to recover from an error may drop out of a
RAID.

FWIW, here is an excerpt from a Seagate technology paper:

Seagate Briefing: Optimizing Surveillance DVR Reliability:
http://www.axetech.be/Pdf/Accessoire...35%20QandA.pdf

"Perhaps surprisingly, complete data integrity for video is not
vitally important. That’s because a small error introduced into a
video stream doesn’t compromise the overall integrity of the visual
image. While a small, perhaps imperceptible, flaw may occur, the
overall video is still intact. However, in order to manage the vast
amounts of video and related metadata in a surveillance system, a
keyed relational database or similar traditional data organizational
system is often used. It is absolutely critical that reads and writes
for such systems employ the utmost levels of error correction and
detection to ensure data integrity isn’t compromised.

An important feature of the SV35 Series disc drive is its support of
the ATA-7 streaming command set. ATA-7 is a recent extension of the
industry-standard ATA command set for controlling disc drives. The
streaming component of this standard enables the SV35 Series drive’s
reads and writes to be customized for either video or data payloads.
Using the ATA-7 streaming commands, both of these requirements are
elegantly met."

Section 4.3 of the following document lists the supported ATA commands
for Seagate's video surveillance models.

SV35 Series SATA Product Manual, Rev. D:
http://www.seagate.com/staticfiles/s...100562053d.pdf

These ATA commands include the following:

Read DMA (C8h)
Read DMA Without Retries (C9h)
Read Sectors (20h)
Read Sectors Without Retries (21h)
Read Verify Sectors (40h)
Read Verify Sectors Without Retries (41h)
Write DMA (CAh)
Write DMA Without Retries (CBh)
Write Sectors (30h)
Write Sectors Without Retries (31h)

- Franc Zabkar
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  #10  
Old June 30th 11, 03:08 PM posted to comp.sys.ibm.pc.hardware.storage
Arno[_3_]
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Posts: 1,425
Default WD AV drives not for desktop use

Franc Zabkar wrote:
On Sun, 26 Jun 2011 22:59:57 -0700, Ed Light put
finger to keyboard and composed:


http://www.techarp.com/showarticle.a...tno=659&pgno=4


AFAICS, that author of that article is misinformed.


AIUI, the drive only skips over bad blocks when its Streaming Command
Set is enabled. The drive still supports the regular command set. In
fact, these commands *must* be used whenever the file system is
updated. The user of an AV-GP drive may not care about a dropped video
frame, but he must have confidence that his file system is intact.


Hmmm. Possible. Sounds even likely.

Furthermore, a drive that supports TLER (Time Limited Error Recovery)
is to be preferred over non-TLER capable drives in RAID environments.
A drive that takes too long to recover from an error may drop out of a
RAID.


Depends on teh RAID. With Linux Software RAID that is not a problem.
For some Hardware RAID cards with old firmware, it is. But basically
TLER is a scan to allow the manufactuers to ask more money for the
same drive with some minor firmware changes.

FWIW, here is an excerpt from a Seagate technology paper:


Seagate Briefing: Optimizing Surveillance DVR Reliability:
http://www.axetech.be/Pdf/Accessoire...35%20QandA.pdf


"Perhaps surprisingly, complete data integrity for video is not
vitally important. That?s because a small error introduced into a
video stream doesn?t compromise the overall integrity of the visual
image. While a small, perhaps imperceptible, flaw may occur, the
overall video is still intact. However, in order to manage the vast
amounts of video and related metadata in a surveillance system, a
keyed relational database or similar traditional data organizational
system is often used. It is absolutely critical that reads and writes
for such systems employ the utmost levels of error correction and
detection to ensure data integrity isn?t compromised.


An important feature of the SV35 Series disc drive is its support of
the ATA-7 streaming command set. ATA-7 is a recent extension of the
industry-standard ATA command set for controlling disc drives. The
streaming component of this standard enables the SV35 Series drive?s
reads and writes to be customized for either video or data payloads.
Using the ATA-7 streaming commands, both of these requirements are
elegantly met."


Section 4.3 of the following document lists the supported ATA commands
for Seagate's video surveillance models.


SV35 Series SATA Product Manual, Rev. D:
http://www.seagate.com/staticfiles/s...100562053d.pdf


These ATA commands include the following:


Read DMA (C8h)
Read DMA Without Retries (C9h)
Read Sectors (20h)
Read Sectors Without Retries (21h)
Read Verify Sectors (40h)
Read Verify Sectors Without Retries (41h)
Write DMA (CAh)
Write DMA Without Retries (CBh)
Write Sectors (30h)
Write Sectors Without Retries (31h)


Ok, so these AV drives are _not_ a problem in normal operation.

Arno
--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
 




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