[PVE-User] openiscsi with Proxmox

[Michael Rasmussen]

On Thu, 2 Jan 2014 16:10:28 -0200
Fábio Rabelo <fabio at fabiorabelo.wiki.br> 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

Get my public GnuPG keys:
michael <at> rasmussen <dot> cc
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mir <at> datanom <dot> net
http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xE501F51C
mir <at> miras <dot> org
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--------------------------------------------------------------
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