IT Survey: Preemptive Drive Replacement in RAID Arrays
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I've never heard of this until today. So no we don't do it here nor anywhere else I've worked.
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To follow up, I've never performed it either. But have heard people say that they replace their drives to avoid the urgent rush of a RAID being depreciated, because of a failed drive.
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@DustinB3403 said:
To follow up, I've never performed it either. But have heard people say that they replace their drives to avoid the urgent rush of a RAID being depreciated, because of a failed drive.
Wouldn't it be just as good to have a cold spare on a shelf waiting for a failure?
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I've never done pre-emptive replacement on drives that are showing no errors.
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@DustinB3403 said:
To follow up, I've never performed it either. But have heard people say that they replace their drives to avoid the urgent rush of a RAID being depreciated, because of a failed drive.
Eh? The array is in a degraded state while it's being rebuilt. What's the difference? Are they not running backups?
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I've definitely never heard of this before, and without some solid evidence on how the expense is worthwhile, data loss that is already super low is some how even lower, I wouldn't consider it.
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I don't understand the rational either.
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@coliver said:
@DustinB3403 said:
To follow up, I've never performed it either. But have heard people say that they replace their drives to avoid the urgent rush of a RAID being depreciated, because of a failed drive.
Wouldn't it be just as good to have a cold spare on a shelf waiting for a failure?
I absolutely agree that having a spare drive on the shelf is more effective, than replacing a drive even if it hasn't failed.
Some people simply don't want to understand what has to be performed to rebuild the array when you replace drives just to replace them.
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I'm guessing this isn't exactly what you're referring to but I thought I'd add my experience anyway. I guess it depends on what you mean by "perfectly healthy". One manufacturer might consider a drive perfectly healthy while another might not.
Certain arrays will look at bad blocks to decide to preemptively to stop using a drive and switch to a hot spare if the number of bad blocks has reached a certain percentage and then they will send you a replacement drive. The number of bad blocks that constitutes a drive that is perfectly healthy vs impending failure varies.
I've contacted a vendor before and sent diagnostic logs on arrays that were going to fall off support to analyze drives that hadn't necessarily crossed that line but might raise a few flags to see if I could get some drives replaced.
As for replacing drives that show no signs at all of failing but just replacing due to being a certain age. I've never done this.
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I mentioned this to an associate of mine and he came up with a possible situation where this could matter, but we both agreed it was pretty unlikely.
His reason was, if the labor pool for emergency repair is small to handle all the emergencies that are happening. Of course there are tons of mitigations for this, but I though the general idea had merit.
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@Dashrender Also maintenance on exceptionally expensive to access sites (think weather station in Greenland or something)
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@MattSpeller said:
@Dashrender Also maintenance on exceptionally expensive to access sites (think weather station in Greenland or something)
That still doesn't make sense because of the failure curve of hard drives. We have no idea if the new drive will die immediately or soon after installation. They would then have to have a second maintenance event to replace the failed drive. Now this may happen either way but it makes more sense to wait until the drive actually fails then to preemptively replace it. Especially if you can get months to years out of the drive you would have replaced.
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@coliver It makes more sense in that scenario than it does in any other I can think of!
I can think of much better ways to setup a remote station like that - I'm just trying to see if there's a scenario where his advice is actually... good.
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For the hard to access station, they should have spares on a shelf, but in theory, when you buy a drive and store it for 3 years, what happens with the warranty if you put it in and it dies after a month?
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@Breffni-Potter spares are a luxury unless you use them on a regular basis
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@MattSpeller said:
@Breffni-Potter spares are a luxury unless you use them on a regular basis
ala weather station in greenland.
Shipping cannot be easy, so what are they to do?
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@Breffni-Potter said:
For the hard to access station, they should have spares on a shelf, but in theory, when you buy a drive and store it for 3 years, what happens with the warranty if you put it in and it dies after a month?
It would be out of warranty. But this wouldn't be the situation as @MattSpeller is describing. If they only visit the site say once every 3 months, presumably they would bring drives with them.
But really, you wouldn't setup a system that relied on this type of solution in this scenerio, you'd choose something with more robustness built in. Though I can't tell you what that would look like. Perhaps 2 or even three equal sized arrays kept in sync with redundant data paths, etc. If the data is that important, but you can only visit the site once every three months, you can't just use the day to day setup in most cases.
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@Breffni-Potter Oh! Yeah I totally agree - that scenario leads to lots of unusual setups
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@Dashrender exactly, there are much better ways to set that kinda thing up - I think we're still looking for a scenario where dude-buddy-guy from SW forums would be right. He may just be 100% wrong.
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I confess to enjoying "devil's advocate" and thought experiments a lot
