Re: How about a behavior...

On 6/24/2025 13:45, Warner Losh wrote:
> On Tue, Jun 24, 2025 at 11:36 AM Jan Bramkamp<crest@rlwinm.de> wrote:
>> On 22.06.25 03:41, Joe McGuckin wrote:
>>> .. where ifs puts drives to sleep in periods when little usage, like after business hours.
>>>
>>> Joe
>> You can do this for SAS or SATA drives with camcontrol, but for spinning
>> disks you shouldn't configure it too aggressive because spinning up will
>> take several seconds and puts wear and tear on the drives and for SSDs
>> it's not that useful.
> Yea. To make this work out, you have to somehow limit the normal 'housekeeping'
> access to the drives from the 'application' data. 'housekeeping' access would
> fail if the drive was spun down, but 'application' data accesses. But
> we don't have
> anything like this in place today.
>
> Warner

I do this here but as Warner said you have to go find all the 
"automated" things (e.g. smartmontools is one of them) that will spin 
them back up and modify their behavior.  Repeatedly up/down is not so 
good; better to leave them spinning in that case.

I have a decent number of "near-line" drives that are rarely accessed -- 
on average they wind up spun up a couple of times a day, and have a 
decent timeout ("camcontrol idle da... -t 1200") which I set out 
of /etc/rc.local at boot-time.  Works fine but again you have to make 
sure any "housekeeping" stuff doesn't immediately spin them back up or 
you're doing more harm than good.

Also check your HBA settings for batching spin-up; you probably want to 
stagger spin-up to a small degree but that too is a trade-off between 
how long before they're online when access is requested .vs. surge 
demand on the supply rail for spin-up.

-- 
Karl Denninger
karl@denninger.net
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