Scale ARC after reboot

[flammen]

This might be a very basic question:

Ist the ARC always completely lost after each reboot? Does each file, which has been in the ARC before the reebot, need to be requested again to be loaded back into the ARC?
I do understand that the ARC is living on memory which is volatile storage - however I would expect that the ARC is indexed somehow and rebuild automatically after a reboot.
I would love the hear why it is not.

Thank you!

 

[spuky]

Because maintaining an copy and index on disk would hurt performance..
and reboots are pretty infrequent so not worth the effort...

you are probably reading a lot of different data after the reboot so why maintaining
(vms are booting jails are starting reading stuff they don't read during normal operation...)

and restoring something that would be replaced by other data right away... does not make much sense...

also the reboot could be caused by a memory error... so what would be the point of restoring a problem

so lots of reasons why that is not done...

l2arc on SSD (which you need to read up on a lot and you probably don't need so don't jump to it without knowing if it fits your usecase) is persistent

 

[flammen]

Because maintaining an copy and index on disk would hurt performance..
and reboots are pretty infrequent so not worth the effort...

you are probably reading a lot of different data after the reboot so why maintaining
(vms are booting jails are starting reading stuff they don't read during normal operation...)

and restoring something that would be replaced by other data right away... does not make much sense...

also the reboot could be caused by a memory error... so what would be the point of restoring a problem

so lots of reasons why that is not done...

l2arc on SSD (which you need to read up on a lot and you probably don't need so don't jump to it without knowing if it fits your usecase) is persistent

Thank you for explainig it, this makes sense to me. Seems to be a well thought out system, this truenas ;)
Have a good day!