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Old 03-27-2008   #11
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Default Re: 24/7 hard drives

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I presume your disks are in some sort of redundant array? That will extend your MTBF. If you're not, then that will certainly decrease your MTBF .
Actually, you're more likely to have an issue with the more drives you have. Statistically, MTBF will decrease with more drives.

Which one is less likely to have problems: a single engine airplane or a twin engine airplane? One would think that the twin would be less likely...but there are more opportunities for something to happen (twice as many, in fact).
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Old 03-28-2008   #12
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Actually, you're more likely to have an issue with the more drives you have.
I think this is the case for me. I probably have in excess of 20 hard drives scattered around the various machines, and now that I have two servers running in the house, each with 4 drives, failure rate is bound to be higher.

Still, I think Windows Home Server eats hard drives, since it churns them constantly.
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Old 03-28-2008   #13
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Still, I think Windows Home Server eats hard drives, since it churns them constantly.
It's not swapping or something, is it? That seems excessive for a server. Out of curiosity, I checked HD activity on one of my office Dell servers providing fileshares and activity was fairly sporadic with Win2003 Server.
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Old 03-29-2008   #14
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It's not swapping or something, is it?
WHS does something called "balancing storage," and if you use the WHS box for anything but backing up the PCs to which it is attached, it will "balance storage" constantly.

Balancing Storage... How does it work? - Windows Home Server Community Forums

The more I use WHS, the more I realize that it's really not even up to the standards of a "1.0" release. It should not be used by folks for anything other than backing up, IMO. There are file corruption bugs, as noted here:

Outrage... (corrupted files) - Windows Home Server Community Forums

MS is not denying the bugs, either:

When certain programs are used to edit or transfer files that are stored on a Windows Home Server-based computer that has more than one hard drive, the files may become corrupted

How do you like that? A server that corrupts files that are written to it. It's not like the thing is designed to make toast and is doing "serving" on the side, now, is it?

And to top it all off, WHS has another bug (feature?) that has the OS throw errors and warn about data loss if a directory structure plus file name goes deeper than 260 characters. Apparently this is a limitation of the .net platform. But so what?

There was a good reason MS kept this thing low profile.
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Old 03-29-2008   #15
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There was a good reason MS kept this thing low profile.
Well, on behalf of someone who is looking to redesign his home network, including tying all of the music, DVD, and home automation together: thank you for the testing and feedback. I won't be going in THAT direction.
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Old 03-29-2008   #16
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I won't be going in THAT direction.
Microsoft is apparently promising an SP1 of WHS for middle of this year. I wouldn't touch it before then.
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Old 03-29-2008   #17
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Default Re: 24/7 hard drives

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Actually, you're more likely to have an issue with the more drives you have. Statistically, MTBF will decrease with more drives.

Which one is less likely to have problems: a single engine airplane or a twin engine airplane? One would think that the twin would be less likely...but there are more opportunities for something to happen (twice as many, in fact).
I don't get that. Why would you have less MTBF if you have more drives in a redundant array? If you have one disk then when that dies you're in doodoo, if you have two or more disks in a redundant array then when one disk dies you're still OK.
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Old 03-29-2008   #18
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I don't get that. Why would you have less MTBF if you have more drives in a redundant array? If you have one disk then when that dies you're in doodoo, if you have two or more disks in a redundant array then when one disk dies you're still OK.
The ARRAY is okay...not the drive.

Keep in mind that MTBF is nothing more than an educated guess, based on the component wear and what the engineers think will probably happen. And "mean" of MTBF is really nothing more than "average"....which means 50% of the failures will (statistically) happen before the MTBF is reached. Of course, no one ever bothers researching the MTBF after a production run has been completed. I'm not even sure it's possible.

Regardless, statistically, the more you have of something, the more likely it is that something will go wrong with ONE of those things. You're four times more likely to get a flat tire in a car compared to a unicycle or twice as likely compared to a motorcycle. There are more opportunities for something to go wrong.

That doesn't mean that having more disks in an array is bad. It merely means that the likelihood of a problem is increased by every disk you add. A well designed array in a production environment should be able to tolerate a two disk or better failure, imo. I usually designed production servers with RAID 10 (now referred to a RAID 6, I believe) using a minimum of seven disks. Each set of two disks was mirrored and the three sets were set up in a RAID 5 with a hot spare. Overkill? You bet. But I worked in an environment where downtime was measured in $10K's per hour. An extra 2-3 $500 disks was cheap insurance.
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Old 03-29-2008   #19
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Default Re: 24/7 hard drives

Well quite, which is why I said "I presume your disks are in some sort of redundant array? That will extend your MTBF. If you're not, then that will certainly decrease your MTBF".

What you say about statistically being more likely to have a physical disk failure when you have multiple disks is obviously correct, but if the data is redundant - i.e. duplicated in some way across multiple disks - then the single instance of a disk failure is less catastrophic than if the data were stored on a single disk as the data is still available. I won't bore you or anyone else with MTBF statistics based on RAID configuration, but a useful site (if you can't get to sleep) is this one:

Storage Advisors Blog Archive RAID reliability calculations
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Old 03-30-2008   #20
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Default Re: 24/7 hard drives

Damn........ I've just replaced my 6yr old Seagate with a WD. I get the impression that I should be backing up on a daily basis for the foreseeable future.


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