So... Scrub isn't lightning fast

Op 30 sep. 2012 om 00:58 heeft Richard Elling 
<[email protected]> het volgende geschreven:

> On Sep 27, 2012, at 5:15 PM, Reginald Beardsley <[email protected]> wrote:
> 
>> --- On Thu, 9/27/12, Richard Elling <[email protected]> wrote:
>>>> 
>>>> zfs_scrub_delay = 100
>>> 
>>> a bit extreme, but probably ok
>>> 
>>>> zfs_scan_idle = 1000
>>> 
>>> no, you'll want to make this smaller.
>> 
>> OK, Thanks.
>> 
>>> Weekly scrubs are a bit extreme. Is your hardware unreliable
>>> enough that you need
>>> to scrub weekly?
>> 
>> No reliability problems except for a 3 TB drive scratch drive that failed.  
>> I only discovered that when I was forced to reboot after a long power 
>> failure. Both Sol 10 U8 and OI 151 have endured several power losses due to 
>> bad UPS  w/o a hiccup.
> 
> It is not likely a scrub will detect this. scrubs are mostly good for 
> detecting
> media problems and phantom writes. There are a whole bunch of other
> failure modes (eg spinup) that scrubs won't exercise.
> 
>> This is new territory. I've never had the ability to check the disk 
>> integrity before.  So what is a sensible scrub schedule?  Monthly?  System 
>> runs 24x7 unless I lose power or a particularly big thunderstorm is coming 
>> through in which case I'll shut down and disconnect the cables.  It's on a 
>> UPS, but I'm on a hill in a bunch of tall trees, so it can get pretty 
>> dramatic.  A few days ago I lost 2 fluorescent light fixtures in my shop and 
>> Mom lost a cordless phone.
> 
> Add lightning to the list of things scrub doesn't exercise :-)
> 
> The scrub interval is determined by an acceptable risk of checking for
> errors that scrub exercises. Scrubs will never offer 100% no-risk.
> -- richard
> 
> --
> illumos Day & ZFS Day, Oct 1-2, 2012 San Fransisco 
> www.zfsday.com
> [email protected]
> +1-760-896-4422
> 
> 
> 
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