On Thu, 2 Jan 2014 16:10:28 -0200 Fábio Rabelo <[email protected]> wrote:
> The people who give me help when I was implementing says this :
>
> 16GB of RAM for boot, PLUS 1 GB of RAM for each 1TB os raw disk space !
>
I think this is a bit overrated. I have 16GB of ram in total in my
storage server which is more the adequate to support for a 2 TB storage
(4 x 1 TB in raid 10)
System Memory:
Physical RAM: 16319 MB
Free Memory : 895 MB
LotsFree: 254 MB
ZFS Tunables (/etc/system):
ARC Size:
Current Size: 12289 MB (arcsize)
Target Size (Adaptive): 12290 MB (c)
Min Size (Hard Limit): 509 MB (zfs_arc_min)
Max Size (Hard Limit): 15295 MB (zfs_arc_max)
ARC Size Breakdown:
Most Recently Used Cache Size: 73% 8994 MB (p)
Most Frequently Used Cache Size: 26% 3295 MB
(c-p)
ARC Efficency:
Cache Access Total: 1032255371
Cache Hit Ratio: 97% 1007543358
Cache Miss Ratio: 2% 24712013
REAL Hit Ratio: 92%
Data Demand Efficiency: 99%
Data Prefetch Efficiency: 4%
> mainly in the SSD ZIL/L2ARK disks ...
>
According to Jeff Bonwick you should always opt for more RAM if this is
possible over SSD ZIL/L2ARC; RAM will always be faster than disk.
Also note that ZIL is not a write cache since write cache happens in
ram. ZIL only purpose is to protect your data so in that respect your
ZIL should always be in raid 1 ->
http://nex7.blogspot.dk/2013/04/zfs-intent-log.html
I can highly recommend this article
(http://constantin.glez.de/blog/2011/02/frequently-asked-questions-about-flash-memory-ssds-and-zfs)
if you want an in-depth knowledge into ZIL and L2ARC and whether this
will help you or not. napp-it provides two scripts for helping you with
this decision zil-stat and arc_summary. Since my ghost measures show 0%
I will not benefit from L2ARC and my current write load does not imply
the need for a ZIL either but should this rise due to heavy database or
file write load I might reconsider.
--
Hilsen/Regards
Michael Rasmussen
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mir <at> datanom <dot> net
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mir <at> miras <dot> org
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