zfs very poor performance compared to ufs due to lack of cache?

Steven Hartland killing at multiplay.co.uk
Sun Sep 5 13:29:43 UTC 2010

> ----- Original Message ----- 
> From: "jhell" <jhell at DataIX.net>
>> Attached is the needfree patch mentioned in the URL alongside a local
>> system patch to adjust kern.maxusers to no more than 512 on systems that
>> can support it...

No joy, still drops down to arc_min even with those two patches and changing
to vm_paging_needed from the post Artem mentioned:

So I suspect if I hadn't put in a high arc_min as well it would be back down
at silly low levels.

top shows:-

Mem: 26M Active, 1360M Inact, 2434M Wired, 6188K Cache, 418M Buf, 117M Free
Swap: 4096M Total, 15M Used, 4081M Free

ARC Size:
        Current Size:                   57.14%  2048.00M (arcsize)
        Target Size: (Adaptive)         57.14%  2048.00M (c)
        Min Size (Hard Limit):          57.14%  2048.00M (c_min)
        Max Size (High Water):          ~1:1    3584.00M (c_max)

So there's still 1.3G of mem sitting inact, don't know what caused that but
its essentially dead memory now it seems.

I know I could raise arc_min even further but that could be dangerous?

Any other suggestions? It seems like arc needs to cooperate with the
rest of the OS pagedaemon more?


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