I have a travel NAS made of small itx computer with large capacity HDD. Because I was concerned about data rotting issue, I installed NAS4Free, cut the HDD into 10 partitions and made a ZFS RaidZ1 vdev. The drive was Seagate Archive 8Tb and it died just after about 4 month. For some reason, the system was writing something on the hard drive continuously, without any stops. It had Owncloud installed, with all it's files (system and data) stored on ZFS dataset.

Now I am replacing the hard drive with WD, so my question is: how much does such a setup affect the HDD lifetime? I am sure the mechanics should wear out faster, but not sure how bad it is exactly.

  • "cut the HDD into 10 partitions and made a ZFS" - this is your issue. The whole point of ZFS is to keep data on different PHYSICAL devices. If you keeping all of your money with you in different pockets, it will not protect you assets if some hooligan rob you, you will loose everything, but if you keep some money in a bank and some of it at home, well you get the point, the same with ZFS. You put heads of HDD in situation where it should constantly moving between partitions and all of it is useless since if hdd fail - you will loose everything regardless redundancy you set – Alex Feb 19 '17 at 6:44
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    By creating a RAIDZ1 (RAID 5) on a single disk, you made it experience three times the seek load. That’s not what the Archive HDD is made for and probably what effectively killed it. If you want single-disk redundancy, use the copies option. 50% storage efficiency is still plenty if you’re concerned about safety. – Daniel B Feb 20 '17 at 10:15
  • @DanielB would something like WD Purple be a better choice for such setup? They position it as a drive for continuous read-writes, like in video surveillance systems. – Anton Lyubinin Feb 21 '17 at 3:41

Putting more than one leg of a RAID set (no matter which level) on the same disk is a bad idea:

  • the only errors it might catch are abd sectors
  • this is by far outweighted by the immense head positioning load

With 10 partitions you will see an over 10fold increase in positioning load, when raid scrubbing jumps in you will see persistant drive activity over days, months or years.

If you care about bitrot: ZFS will detect that even with a single leg due to checksumming. The chance of it being able to correct it with a single leg is zero, but the important part is, that this chance doesn't increase dramatically with another leg on the same disk: The probability of the disk failing prematurely due to the increased stress by far overweighs the chance of a correctable error due to localized sector falure.

  • How can ZFS take care of that with a single leg with no redundancy? I only know of the "copies" option, but that is essentially mirroring and reducing the storage at least 2 times – Anton Lyubinin Feb 19 '17 at 4:45
  • ZFS employs 256 bit checksums end-to-end to validate data stored under its protection. But using ZFS on a single drive as was said by CTO of iXsystems - something like "single disk ZFS is so pointless it's actually worse than not using ZFS" – Alex Feb 19 '17 at 6:46
  • @Alex: The purpose of StackExchange community is to provide qualified answers (in polite form) to the questions. Not the quotes from WTFIS that you don't even seem to understand. "It is pointless" exactly because checksums provide no way to restore your data, so using ZFS with vdev, consisting of 1 hdd, provide no redundancy. Now, no matter who said what, there are good reasons to use ZFS even in such setup. – Anton Lyubinin Feb 19 '17 at 7:36
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    @Alex I don't know the exact quote you've related to, but the statement you made is debatable: even a single basic vdev detects bit rot and partial hard drive failure like Unrecoverable read errors (URE). It cannot correct them without a second disk, but detection helps you to know what is up with your data (so you can make separate backups etc). – user121391 Feb 20 '17 at 8:09
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    @Alex Sorry, my comment was unclear. I was only focusing on your last sentence (which I also edited), the rest I agree with. – user121391 Feb 20 '17 at 10:26

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