How often to run Scrub/Smart Tests?

[Protopia]

@Stux

The point that eric and myself are trying to get across is that scrubs are going to be slower once the disk is full as the scrub process has to bounce between reading metadata and reading blocks.

Ah yes - those seeks and rotational delays would likely make a scrub substantially slower.

[matchaman]

What I meant more so it’s not easy to define the scrub to run the 1st and 3rd weeks and the long to run the 2nd and 4th weeks. I am hoping I have that set, but not really a way to define that unless you go through and set dates manually. Instead of doing that I have it set for different days of the week so even if they do run the same week, it shouldn’t overlap. Otherwise I do have different smart tests scheduled (short daily, long weekly)

[moelassus]

How do you set fixed dates?

[chuck32]

You can set the schedule to custom and then just enter the dates instead of cron job notation.

[sfatula]

My preference is to run the scrubs weekly to catch any errors quicker. My pool takes 7 hours so it runs fine overnight. Disk temps don’t even change.

[Davvo]

The latter part of Assessing the Potential for Data Loss talks a bit about scrubs.

Iirc I run one every 5 or 6 weeks; when data is read ZFS automatically corrects any error if it has enough parity. I also run daily short tests and weekly long ones in order to catch any issues with the drives.

Crucially, I run ECC hardware.