Western Digital AV-GP 2 TB Hard Disk Drive Review

Discussion in 'Reviews & Articles' started by Adrian Wong, Feb 25, 2010.

  1. ZuePhok

    ZuePhok Just Started

    nope. one day file copy went really slow.

    and since then it's been very difficult to retrieve data out of it.

    i gave up! :wall:
  2. Tiggle

    Tiggle Newbie

    AV-GP good for media servers

    I'm posting to dispute the review on techarp for the AV-GP drive that claims is should not be used for desktops or servers. The review makes it sound as if this would be a terrible mistake as data would be corrupted during every day use.

    After reading whatever I can get my hands on, which isn't much, I have to say I disagree. An AV-GP might not be the best choice for a file server or desktop, but it is not true that it should or could not be used in one. My understanding is it functions as a normal drive, it just has some extra streaming features. The stream commands are not used all the time and should not result in data loss during normal operation. I have not read anywhere else that these drives should not be used in any particular application. On the WD product page it even lists media server as one of the recommended applications. In a review link on the WD product page, it references a system that uses an AV-GP drive to build an HTPC. This requires the OS live on that drive.

    The AV-GP also boasts sustained operation in higher temperature environments. Increased reliability during long term use certainly appeals to me. The more I read, the more I think this drive is ideal for a media server. Also, it was suggested that retailers could be unscrupulous or mislead by selling the drives for a higher cost, as if they are faster. Faster, probably not, but worth a little more, definitely. The drive has extra features and would seem to be the product of extra engineering effort.

    If you read the review, I recommend taking it with a grain of salt. I am not confident the reviewer really knows the facts and the result is a misleading review.

    I welcome feedback and debate on the subject. I am considering a couple of these to build a media server myself. I would very much like to get the facts straight before making my decision.


  3. Falcone

    Falcone Official Mascot Creator

    Hahaha welcome to the club, had to RMA mine....still have to wait a couple more weeks to get it back.
  4. Adrian Wong

    Adrian Wong Da Boss Staff Member

    Hello Tiggs,

    It is a fact that AV-type of drives improve streaming performance by restricting the command completion time. In the event a write takes longer than the desired completion time, it gets "cut". That's okay for AV-type of applications since you do not need every pixel in the image to be "correct". However, that is not something you want happening in other applications - file server, desktops, etc.

    Will the AV-GP (or other AV-type HDDs) write bad data all the time? No, of course not. Will that happen once in a while? That depends.

    If every read / write command can be satisfied within 100 ms (or so), then they will be read / written correctly. However, the drive is designed to complete all reads and writes within the stipulated time. If there's a CRC error or bad sector that causes the drive to exceed the command completion time, the drive is designed to just "forget" about that particular read/write command and continue to the next one.

    Sure, you can use AV-type HDDs to build anything. No one is stopping you. These drives should have no problem running in HTPCs and media servers, since operating systems are generally write once affairs (except for the occasional patches or updates), and any media playing off the HTPC (or a media server) will not exhibit any noticeable quality difference. Even if the AV-GP drive ignores a few bits per frame, you won't spot the bad pixels in the image.

    I can understand why you think I'm wrong in this matter, although I disagree with you. If I'm wrong, I would be more than happy to correct the review. However, if you aren't even sure, why are you labelling it as a misleading review? I would appreciate something more than just a "feeling". If you know something we don't, please let us know.

    BTW, I did not say that some retailers could be unscrupulous by selling the AV-GP drives at a higher cost. What I said specifically was "Some unscrupulous or misinformed dealers are promoting such AV-optimized hard disk drives as "superior" versions of their desktop cousins with appropriately higher price tags."

    I have encountered retailers actually recommending AV-type drives over regular desktop drives for their "superior quality" or "superior performance". No, they did not just sell them at a premium. They outright labelled the AV-type drives as "superior", or claimed these drives are "superior" or "faster" when asked about the difference between AV and regular HDDs. There's a difference.
    Last edited: Apr 9, 2010
  5. Tiggle

    Tiggle Newbie

    Hello Adrian,

    Thanks for the detailed reply.

    I think my confusion or concern about the drives comes in with the streaming commands. Does the drive always cut error correction short if it runs out of time? Or does the error correction problem only occur when the streaming commands are used? When are the streaming commands used? Does an application have to be written to use streaming commands, etc?

    Sorry if I misquoted you or took your words out of context. I didn't mean to offend.

    Do you have more information about how and when the drive uses the streaming commands? Would an OS really be subject to problems using this drive because of the error correction behavior? I see good reviews on Newegg from people who bought this drive and seem to have used it for normal desktop applications. There are no reports of errors, or bad experiences. Could it be they do not have a supporting controller to use the streaming commands, or maybe the problem has just gone unnoticed up to this point?


  6. Adrian Wong

    Adrian Wong Da Boss Staff Member

    We should get Mike from WD here to provide the full technical details. But as far as I know, yes, all error corrections will be cut short to meet the 100 ms time limit (in the GP-AV drive).

    The drive controller must support the ATA streaming commands. As I understand it, if both drive and drive controllers support the ATA streaming commands, they are enabled by default, even when used in desktops. This is because you can use a desktop to manage CCTV feeds and record the video streams to the AV HDD.

    The problem is I don't think the ATA streaming command actually affects the time limit for error correction. Look at this. From what it states, the specific time limit is already in place. The Read Continuous and Write Continuous commands merely log the errors so if necessary, error correction can be performed later.

    No, you did not offend. I'm merely pointing out that it is not the high price that is the issue here. The issue is when folks ask these unscrupulous retailers why are these drives are more expensive, they will be told that these drives are either superior in quality or run much faster than desktop HDDs.

    I don't think read operations will ever be a problem for these drives. Unless you get hit by a bad sector, all read commands will be easily satisfied within the time limit. Look at our benchmark results.

    The random access time (read) is only 33 ms, far below the 100 ms time limit. The sequential access time (read) is even less, at just 5.2 ms. So no, most of the time, I don't think the time limit will come into the picture. The trouble is what happens if there's a write / read error that takes too long to correct?

    Again, look at the benchmark results. Compared with the Caviar Green, the desktop version of the AV-GP, the AV-GP is faster at one thing - large, sequential reads and writes, just the thing media servers and CCTV systems need. On the other hand, the desktop Caviar Green is much faster at small sequential transfers and large random transfers.

    Based on that kind of performance, I would rather go with the desktop Caviar Green, if I'm building a desktop PC or a file server. The Caviar Green is also cheaper, and if our temperature readings are accurate, much cooler to run.
  7. Tiggle

    Tiggle Newbie

    Thanks Adrian

    I really appreciate you taking the time to talk this over with me. From the sound of things, I would be better off with a regular GP drive. I must admit, I was hoping the AV drive would provide a nice improvement for my home media server, but after talking about it, I am not convinced it would be the best decision.


  8. Adrian Wong

    Adrian Wong Da Boss Staff Member

    No problem. BTW, Mike from WD just confirmed it. To summarize :

    1. The time limit for error correction is preset for these AV-type drives. It prevents the drive from hanging/recovering too long while recording. Otherwise, you will lose a few seconds of video.

    2. ATA Streaming Commands won't change the time limit.

    3. The AV hard disk drive has a different hardware and is tested at a higher temperature limit, thus a higher temp spec.

    4. With or without ATA streaming command support, the drive is still optimized for AV purposes e.g. recording/playing back up to 12 HD streams simultaneously

    Well, if you are only looking to serve video files on your home media server, the AV-GP hard disk drive should run just fine. It will ensure that your video streams will never get disrupted by error correction. This is important if you also intend to record videos directly to the server (perhaps from satellite TV).

    The time limit for error correction will usually not cause any problems since you won't actually write critical data to the HDD, e.g. office documents, original copies of family photos (without backups elsewhere), etc. I just don't recommend it for desktops, or file servers, or any situation where it will store the ONLY copy of any data you have.
  9. E.B.E.

    E.B.E. Newbie

    Sorry to bring an old thread back from the dead, but this review is still one of the first results that comes up when searching for the issue of error correction in AV-GP models. It almost cost me canceling my order for 2 of these harddrives today before I did more thorough research.

    To the point: I have looked at the ATA standard and the "silent" errors (and their timeouts) ARE INDEED controlled by the streaming command set, and only allowed when these commands are used. Have a look in Section 4.24 of the standard: (google for d2015r1a-ATAATAPI_Command_Set_-_2_ACS-2.pdf, sorry, can't post links). A so-called stream is created, associated with an error limit; and then the streaming read/write commands work on this stream, and are affected by this limit, and may be configured so as to silently skip errors.

    Now this does not mean that the drive doesn't have shorter-than-normal error recovery time limits (similar to e.g. the TLER in the Enterprise-class drives); perhaps that's where the misunderstanding stems from. In any case, whatever the time limits may be, when using the regular ATA commands the standard does NOT allow the drive to make a silent error (see e.g. section 7.27, READ DMA command), which is the whole point and what is being so dramatically emphasized in the review. Then knowing an error has occurred, the OS can take over and request a re-try of the command or whatever measure is appropriate.

    So on this topic I do still think the review is written in an overly alarming tone, and for the sake of other people looking for this info, that section should be qualified with the correct information.
  10. Adrian Wong

    Adrian Wong Da Boss Staff Member

    Hi E.B.E.!

    First of all, for the benefit of everyone here, the document you are referring to can be found @ http://www.t13.org/documents/UploadedDocuments/docs2009/d2015r1a-ATAATAPI_Command_Set_-_2_ACS-2.pdf

    Also, you might want to look at the Hitachi whitepaper @ http://www.hgst.com/tech/techlib.nsf/techdocs/FEF3B52BFE9A054586256E66005AA389/$file/WP_AV_25March.pdf

    If you look at the overview of the Streaming feature set, it states (emphasis my own) :

    Then, look at Write Continuous bit, which states (again, emphasis my own) :

    Thus, I think the emphasis is justified. I've seen many people actually think that the AV drives must be better (faster?) or more suited for multimedia applications. Some (misguided? unscrupulous?) dealers even tell them so. That's just not true.

    These drives are good for applications like CCTV systems and DVRs, but definitely should not be used where absolute data integrity is necessary.
  11. E.B.E.

    E.B.E. Newbie

    Hi, and thanks for the fast reply!

    All the information in your post is correct, and corresponds to the information in my 2nd paragraph.

    However, the review information is different (and still incorrect) in that it suggests this behavior will happen with the harddrive in desktop use.

    In fact, the behavior only appears when using these streaming commands. In desktop use, the SATA controller will in all likelihood issue the regular ATA read/write commands (such as the READ DMA I was exemplifying in the previous post), in which silent errors are explicitly not allowed by the standard.

    Hope this clarifies.
    Last edited: Jul 10, 2012
  12. Adrian Wong

    Adrian Wong Da Boss Staff Member

    Good point! Let me verify this with WD and get back to you.
  13. E.B.E.

    E.B.E. Newbie

    OK thanks!
    By the way, I got the two 3TB AV-GP harddrives I was mentioning and put them through the paces. The tests were:
    - surface check with Windows 7 chkdsk
    - formatting with TrueCrypt (writes random data to the entire HDD)
    - formatting with a Synology NAS (involves another surface check)
    - writing large amounts of data, after which I made some random file selections and checked them by content, byte-by-byte, against the original.

    No issues whatsoever. The drives are virtually silent, you have to touch them to realize they are running. A bit slow to spin up, but this does not really affect performance in the media storage role that as I use them for.
  14. Junsas

    Junsas Newbie

    Hi Adrian,

    did you ever get a final statement from WD?
  15. Adrian Wong

    Adrian Wong Da Boss Staff Member

    Not yet. Let me check with them again.
  16. envoid

    envoid Newbie

    I, too, was brought to the site as your review is one of the first from a Google search while questioning the reality of the data integrity for regular files. Everything is starting to seem as if the streaming commands are what set the error recovery (though I'm sure they have TLER at a lower number as well). WD's description for their SilkStream feature also insinuates that it is based on the command set.

    Taken from their AV-GP product page (wdc.com../en/products/products.aspx?id=150 (remove the ..)) under the "More Features" grey bar.

    And after reading the HGST paper and some of the T13 document, more and more it seems like the AV-GP drives are regular GP drives tweaked a little for sequential read/writes while also supporting the ATA Streaming Commands set (and 3yrs warranty compared to the 2yrs for normal GP).

    I would be surprised if WD came back and confirmed this at all as it would destroy their marketing of the drive as an "AV-only" drive, but still would like them to comment on this. The WD source was pretty vague with #4...

    This could just reinforce the sequential read/write optimizations. Also, #1 & #2 could reinforce the low TLER setting (if it can be changed with their tool then even bigger disaster for them).
    I have two 2TB EURS drives coming today, I plan on checking to see if the tool reads the setting and can change it. I will try to follow-up here (if i promise things seem to always get in the way).

    An aside, thank you for your review of the drive and being open to talk about this!
  17. Adrian Wong

    Adrian Wong Da Boss Staff Member

    Actually, I'm also very interested to clear this up once and for all. Heck, if I'm wrong, then this should also go into the HDD Myths Guide! :D

    No news yet from WD. I will go prod them some more.
  18. envoid

    envoid Newbie

    I tried getting WDTLER to work with the drives but it throws up saying read/write TLER is not supported on them. Doesn't work with my black 500GB I got also (WD5003AZEX). BUT it does work with my older 500GB (WD5002ABYS) so at least I know it was working... :wall:

    This sucks... now I'm curious what other tools might be out there that might work with this. WDIDLE3? Though I'm not sure I care that much since they are serving video in a mirror and only maybe 6hrs a day at most.

    Btw, I used v1.03 of WDTLER (don't know of a newer version).
  19. Adrian Wong

    Adrian Wong Da Boss Staff Member

    You have to be careful with WDTLER because it enables or disables TLER for all compatible HDDs in the system. And WD claims it may damage the firmware for newer HDDs. So I would advise you not to use it.
  20. envoid

    envoid Newbie

    If you just run the wdtler.exe (no switches) it does a scan only. But yeah, you have to be careful as it does it for all drives at once.

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