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HR34 and 4TB External Drive


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131 replies to this topic

#51 OFFLINE   Laxguy

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Posted 20 November 2012 - 11:05 PM

Well, I was pretty good at statistics, and heartily disagree, but I think that's where we'll end up unless a math whiz comes along.
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#52 OFFLINE   RunnerFL

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Posted 20 November 2012 - 11:18 PM

Well, I was pretty good at statistics, and heartily disagree, but I think that's where we'll end up unless a math whiz comes along.


How is a single drive failure different than a single drive failure? :lol:
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#53 OFFLINE   P Smith

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Posted 20 November 2012 - 11:43 PM

Well, I was pretty good at statistics, and heartily disagree, but I think that's where we'll end up unless a math whiz comes along.


You're right , there is clearly demonstrated missing knowledge.

The rule is simple: total reliability is a product of multiplying all part's reliability.

Say one HDD has reliability equal 90% [0.9], then two same HDD will has total 0.81 ie 81%. Any engineer knows that and it shouldn't be discussed here.

#54 OFFLINE   harsh

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Posted 21 November 2012 - 09:07 AM

I'd see it as less reliable than running it off one. If either drive dies, you lose it. It seems to me there is a greater chance of that happening than one drive.

If experience of the hardcore users is any indication, the DVR will likely die before either of the hard drives dies.
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#55 OFFLINE   harsh

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Posted 21 November 2012 - 09:08 AM

Any engineer knows that and it shouldn't be discussed here.

There are few engineers here so it bears repeating.
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#56 OFFLINE   Diana C

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Posted 21 November 2012 - 09:58 AM

You're right , there is clearly demonstrated missing knowledge.

The rule is simple: total reliability is a product of multiplying all part's reliability.

Say one HDD has reliability equal 90% [0.9], then two same HDD will has total 0.81 ie 81%. Any engineer knows that and it shouldn't be discussed here.


True, over the total lifetime of the two drives, and that is the calculation for RAID 0. However, the whole point of RAID 1 is to exploit the fact that the failure of a drive is likely to happen at any point over the entire expected lifetime of the drive (as stated in the MTBF rating). Therefore, the likelihood of both drives failing at the same time is vanishingly small. I honestly don't see the point of RAID 0 in a DVR use case. The DVRs don't need the extra drive performance, and buying two 1TB drives is more expensive than one 2TB drive.

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#57 OFFLINE   dpeters11

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Posted 21 November 2012 - 10:58 AM

If experience of the hardcore users is any indication, the DVR will likely die before either of the hard drives dies.


Very possible. This is one reason I'm not doing a raid setup until the policy changes.

#58 OFFLINE   Rich

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Posted 21 November 2012 - 11:52 AM

Well, I was pretty good at statistics, and heartily disagree, but I think that's where we'll end up unless a math whiz comes along.


Validate that. Tell me what the odds are on hitting a home run the next time you get up after hitting a home run. And if you do hit a home run in successive at bats, what are the odds on hitting a third one?

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#59 OFFLINE   Rich

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Posted 21 November 2012 - 11:54 AM

If experience of the hardcore users is any indication, the DVR will likely die before either of the hard drives dies.


Agreed and that's the problem we all face. Make the HRs and HDDs compatible with each other within an account and the problem goes away instantly.

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#60 OFFLINE   RunnerFL

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Posted 21 November 2012 - 11:55 AM

I honestly don't see the point of RAID 0 in a DVR use case.


Space. 2 x 2TB = 4TB.
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#61 OFFLINE   dpeters11

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Posted 21 November 2012 - 11:59 AM

Maybe WD will have a 4TB AV drive soon, since they have a 4TB Black drive.

#62 OFFLINE   Laxguy

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Posted 21 November 2012 - 12:20 PM

Validate that. Tell me what the odds are on hitting a home run the next time you get up after hitting a home run. And if you do hit a home run in successive at bats, what are the odds on hitting a third one?

Rich


I did say was....!

The odds of me hitting the first homer are vanishingly small, but assuming they are constant, it'd be the same for each successive at bat. That's assuming constancy, of which there's very little in a real life BB. I'd be pitched to differently after astonishing everyone in the ball park on the first homer, and, after the second dinger, clearly walked in my third a.b., or h.b.p.
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#63 OFFLINE   inkahauts

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Posted 21 November 2012 - 11:24 PM

If experience of the hardcore users is any indication, the DVR will likely die before either of the hard drives dies.


That's the exact opposite of what i have seen with my DVrs.

#64 OFFLINE   unixguru

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Posted 22 November 2012 - 09:28 AM

Can the HR line deal with RAID 1? Would this impact performance?


Sure. A "host" (DVR) doesn't know whether it's talking to a single directly connected drive or a fake virtualized drive presented by a RAID controller.

I've been running RAID 1 since the HR20 first came out. First with Sans Digital and the last few years with a CalDigit VR. Never a problem with the HR. Search my posts for details.

There should not be any performance impact for RAID 1. Writes go to both drives at the same time. Reads can come from either drive so reading can actually be faster (for a given block use the drive whose head is the closest minimizing seek time).

Other levels of RAID might negatively impact performance. A cheap/older RAID 5 or 6 array might be slower because of the need to calculate (in the controller) checksums for writes.

#65 OFFLINE   kevinturcotte

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Posted 22 November 2012 - 09:29 AM

Sure. A "host" (DVR) doesn't know whether it's talking to a single directly connected drive or a fake virtualized drive presented by a RAID controller.

I've been running RAID 1 since the HR20 first came out. First with Sans Digital and the last few years with a CalDigit VR. Never a problem with the HR. Search my posts for details.

There should not be any performance impact for RAID 1. Writes go to both drives at the same time. Reads can come from either drive so reading can actually be faster (for a given block use the drive whose head is the closest minimizing seek time).

Other levels of RAID might negatively impact performance. A cheap/older RAID 5 or 6 array might be slower because of the need to calculate (in the controller) checksums for writes.


Even an HR34, writing 5 stream at once, 2 of which might by OTA HD, don't effect performance? I would *THINK* it would, having to "Double write" everything?

#66 OFFLINE   Rich

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Posted 22 November 2012 - 09:32 AM

I did say was....!

The odds of me hitting the first homer are vanishingly small, but assuming they are constant, it'd be the same for each successive at bat. That's assuming constancy, of which there's very little in a real life BB. I'd be pitched to differently after astonishing everyone in the ball park on the first homer, and, after the second dinger, clearly walked in my third a.b., or h.b.p.
:hurah:


Validated! Good for you! And you did it quickly enough to make me believe you didn't Google the answer.

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#67 OFFLINE   Rich

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Posted 22 November 2012 - 09:39 AM

That's the exact opposite of what i have seen with my DVrs.


Over 60 HRs since '06, I've had, and only a couple HDD failures that I was sure of. All the HRs I returned were definitely bad. I guess this is an argument we'll have from time to time. Both valid, both based on experience, but so different... :lol:

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#68 OFFLINE   unixguru

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Posted 22 November 2012 - 10:02 AM

Even an HR34, writing 5 stream at once, 2 of which might by OTA HD, don't effect performance? I would *THINK* it would, having to "Double write" everything?


It would if the double write happened sequentially. It doesn't. The RAID controller sends writes to both drives at the same time.

Disk I/O is not an atomic operation at the device level. It's a command/response situation. Thus command, command, wait, response, response is perfectly normal. The wait (or more accurately wait, wait) time is far larger than the command or response time.

In a small-scale RAID the drives don't even share a physical/electrical channel; each is wired directly to the RAID controller.

#69 OFFLINE   unixguru

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Posted 22 November 2012 - 10:12 AM

Over 60 HRs since '06, I've had, and only a couple HDD failures that I was sure of. All the HRs I returned were definitely bad. I guess this is an argument we'll have from time to time. Both valid, both based on experience, but so different... :lol:


This has probably been discussed before. With a fairly large sample such as this and more non-drive failures than drive failures, I believe you have one or more environmental issues.
  • "Dirty" power
  • Improperly installed dish or wiring (bad grounds, lightning/static sensitivity)
  • Thermal problems (inadequate ventilation, etc)


#70 OFFLINE   Rich

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Posted 22 November 2012 - 10:15 AM

It would if the double write happened sequentially. It doesn't. The RAID controller sends writes to both drives at the same time.

Disk I/O is not an atomic operation at the device level. It's a command/response situation. Thus command, command, wait, response, response is perfectly normal. The wait (or more accurately wait, wait) time is far larger than the command or response time.

In a small-scale RAID the drives don't even share a physical/electrical channel; each is wired directly to the RAID controller.


After having two expensive (~$500) RAID boxes fail within a year I've been kinda leery about them. What is the best one to buy? Best one being the one you'd get if you were buying one today.

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#71 OFFLINE   unixguru

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Posted 22 November 2012 - 10:38 AM

After having two expensive (~$500) RAID boxes fail within a year I've been kinda leery about them. What is the best one to buy? Best one being the one you'd get if you were buying one today.


Hope that price included the drives!

I've gone through 2 older Sans Digital models and would never buy again.

I've had a CalDigit VR for the last 3 years. First on HR20 and now HR34. Love it. Have upgraded drives in it once and will be doing again soon (only trick is you need a special security screwdriver for screws in drive trays). Runs very cool and as quiet as it can be - external power brick. The VR may be limited to 2x2TB so max 2TB RAID 1. (Also configure for "Turbo" mode as it's optimized for video.)

If I had to buy today I'd either get a used VR or the newer VR2. (There is a used one on eBay 4TB for $280 expires in a few hours.)

Unfortunately you can't buy the enclosure without drives. It's relatively expensive. But keep in mind you must use enterprise/RAID class drives so it really isn't unreasonably priced.

Note: CalDigit VR Mini is different model than CalDigit VR

Edited by unixguru, 22 November 2012 - 10:46 AM.
Added warning about "mini" model


#72 OFFLINE   Rich

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Posted 22 November 2012 - 11:25 AM

This has probably been discussed before. With a fairly large sample such as this and more non-drive failures than drive failures, I believe you have one or more environmental issues.

  • "Dirty" power
  • Improperly installed dish or wiring (bad grounds, lightning/static sensitivity)
  • Thermal problems (inadequate ventilation, etc)


Most of the problems were early on and due to HDMI incompatibility with my TVs.

I've been an electrician for many years and I don't have "dirty" power.

Improper installations have been a problem that has caused many of my HR failures.

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#73 OFFLINE   Rich

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Posted 22 November 2012 - 11:33 AM

Hope that price included the drives!


Was awhile ago, but I think they came with two 1TB drives in each one.

I've gone through 2 older Sans Digital models and would never buy again.

I've had a CalDigit VR for the last 3 years. First on HR20 and now HR34. Love it. Have upgraded drives in it once and will be doing again soon (only trick is you need a special security screwdriver for screws in drive trays). Runs very cool and as quiet as it can be - external power brick. The VR may be limited to 2x2TB so max 2TB RAID 1. (Also configure for "Turbo" mode as it's optimized for video.)


I've got all the security screwdrivers. So CalDigit VR, huh? I'll lock that in the vault for future use. Thanx.

Unfortunately you can't buy the enclosure without drives. It's relatively expensive. But keep in mind you must use enterprise/RAID class drives so it really isn't unreasonably priced.


The new WD Red Caviar are recommended for RAIDs and they're not that expensive.

Just curious about the RAID boxes. At the moment, I have nothing I can do with one. But, you never know...

Rich

#74 OFFLINE   inkahauts

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Posted 22 November 2012 - 01:39 PM

Over 60 HRs since '06, I've had, and only a couple HDD failures that I was sure of. All the HRs I returned were definitely bad. I guess this is an argument we'll have from time to time. Both valid, both based on experience, but so different... :lol:

Rich


Hey,I've always said you have a very unique issue. I don't recall seeing anyone else go through as many as you have! :)

But other than fan and power supply, I see no reason for anything else to regularly break in these things anyway. I have a feeling the number one issue that DIRECTV has other than hard drives though is power supply's, and then maybe the fans.

But yeah, everyone is different. I just don't see enough people asking about issues that are likely non hard drive but definitely DVR related to think that hard drives aren't the number one issue by far, after install issues. I think installs are probably the number one issue in general people have with DIRECTV systems.

#75 OFFLINE   unixguru

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Posted 22 November 2012 - 04:56 PM

The new WD Red Caviar are recommended for RAIDs and they're not that expensive.


Wasn't aware of these - thanks. Will have to try them next time I upgrade...




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