[zfs-discuss] zfs-discuss Digest, Vol 43, Issue 3

[George Melikov]

> I believe no answer has been given as to why one should avoid > 4TB drives (or helium-filled disks for that matter). Interestingly, the latest backblaze stats recommend helium-based models.

The answer is short: disk read/write speed is nearly (yes, +-100MB/sec can't help you there) same for every HDD size, so resilver time will grow linearly and 4+TB disk have more risk of pool destruction during resilver.

Cherry on a pie:
- consumer HDDs: Non-recoverable read errors per bits read = <1 in 10^14, so manufacturers are nearly guarantee a one bit failure on ~11.37TB of data read
- enterprise HDDs: <1 in 10^15, so a one bit failure on ~113TB of data read

https://en.wikipedia.org/wiki/RAID#URE

07.11.2018, 17:36, "Maurice Volaski via zfs-discuss" <zfs-discuss at list.zfsonlinux.org>:
>>  IMO, disks much over 4TB are bad news. I suggest you stick with 4TB disks.
>>  Avoid shingled or helium filled disks, or those under 7200rpm. Consult last
>>  few years worth of Backblaze statistics when choosing the disk brand and
>>  model to get.
>
> I believe no answer has been given as to why one should avoid > 4TB drives (or helium-filled disks for that matter). Interestingly, the latest backblaze stats recommend helium-based models.
>
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____________________________________
Sincerely,
George Melikov