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WD AV drives not for desktop use
http://www.techarp.com/showarticle.a...tno=659&pgno=4
-- Ed Light Better World News TV Channel: http://realnews.com Iraq Veterans Against the War and Related: http://ivaw.org http://couragetoresist.org http://antiwar.com Send spam to the FTC at Thanks, robots. |
#2
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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 -- 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 |
#3
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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
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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. -- Ed Light Better World News TV Channel: http://realnews.com Iraq Veterans Against the War and Related: http://ivaw.org http://couragetoresist.org http://antiwar.com Send spam to the FTC at Thanks, robots. |
#5
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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 -- 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 |
#6
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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
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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. -- (\__/) (='.'=) (")_(") |
#8
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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. -- (\__/) (='.'=) (")_(") |
#9
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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 -- Please remove one 'i' from my address when replying by email. |
#10
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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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