Re: Re: Desperate with 870 QVO and ZFS

I have been thinking and.... I got the following tunables now : 

vfs.zfs.arc_meta_strategy: 0
vfs.zfs.arc_meta_limit: 17179869184
kstat.zfs.misc.arcstats.arc_meta_min: 4294967296
kstat.zfs.misc.arcstats.arc_meta_max: 19386809344
kstat.zfs.misc.arcstats.arc_meta_limit: 17179869184
kstat.zfs.misc.arcstats.arc_meta_used: 16870668480
vfs.zfs.arc_max: 68719476736

and top sais : 

ARC: 19G Total, 1505M MFU, 12G MRU, 6519K Anon, 175M Header, 5687M Other


When using even 128GB of vfs.zfs.arc_max (instead of 64GB I have now
set) the ARC wasn't approximating to it's max usable size.... Can
perhaps that could have something to do with that fact that arc meta
values are almost at the limit set?. Perhaps increasing
vfs.zfs.arc_meta_limit or kstat.zfs.misc.arcstats.arc_meta_limit (I
suppose the first one is the one to increase) could cause a better
performance and perhaps a better usage and better take advantage of
having 64GB max of ARC set?. I say it because now it doesn't use more
than 19GB in total ARC memory.... 

As always said, any opinion or idea would be very highly appreciated. 

Cheers, 

El 2022-04-06 17:30, egoitz@ramattack.net escribió:

> ATENCION: Este correo se ha enviado desde fuera de la organización. No pinche en los enlaces ni abra los adjuntos a no ser que reconozca el remitente y sepa que el contenido es seguro.
> 
> One perhaps important note!! 
> 
> When this happens... almost all processes appear in top in the following state: 
> 
> txg state or 
> 
> txg-> 
> 
> bio.... 
> 
> perhaps should the the vfs.zfs.dirty_data_max, vfs.zfs.txg.timeout, vfs.zfs.vdev.async_write_active_max_dirty_percent be increased, decreased.... I'm afraid of doing some chage ana finally ending up with an inestable server.... I'm not an expert in handling these values.... 
> 
> Any recommendation?. 
> 
> Best regards,
> 
> El 2022-04-06 16:36, egoitz@ramattack.net escribió: 
> 
> ATENCION: Este correo se ha enviado desde fuera de la organización. No pinche en los enlaces ni abra los adjuntos a no ser que reconozca el remitente y sepa que el contenido es seguro.
> 
> Hi Rainer! 
> 
> Thank you so much for your help :) :) 
> 
> Well I assume they are in a datacenter and should not be a power outage.... 
> 
> About dataset size... yes... our ones are big... they can be 3-4 TB easily each dataset..... 
> 
> We bought them, because as they are for mailboxes and mailboxes grow and grow.... for having space for hosting them... 
> 
> We knew they had some speed issues, but those speed issues, we thought (as Samsung explains in the QVO site) they started after exceeding the speeding buffer this disks have. We though that meanwhile you didn't exceed it's capacity (the capacity of the speeding buffer) no speed problem arises. Perhaps we were wrong?. 
> 
> Best regards, 
> 
> El 2022-04-06 14:56, Rainer Duffner escribió: 
> 
> Am 06.04.2022 um 13:15 schrieb egoitz@ramattack.net: 
> I don't really know if, perhaps the QVO technology could be the guilty here.... because... they say are desktop computers disks... but later. 
> 
> Yeah, they are. 
> 
> Most likely, they don't have some sort of super-cap. 
> 
> A power-failure might totally toast the filesystem. 
> 
> These disks are - IMO -  designed to accelerate read-operations. Their sustained write-performance is usually mediocre, at best. 
> 
> They might work well for small data-sets - because that is really written to some cache and the firmware just claims it's „written", but once the data-set becomes big enough, they are about as fast as a fast SATA-disk. 
> 
> https://www.tomshardware.com/reviews/samsung-970-evo-plus-ssd,5608.html