Speed Confusion and SSD cache benefits

[Rayworth]

FREENAS SERVER SETUP
Freenas 9.2.1.6
Asrock
motherboard
E3C224D4I-14S
Intel Xeon E1230V3 3.3GHz Processor
32GB Crucial memory CT2KIT102472BA186D.000 2x - 8GB DDR3-1866 ECC.
Hard Drives
1x Samsung 840 128Gb Freenas OS
Hitachi
7x HDS724040ALE640
7200 RPM
Switch Cisco 3750G
LACP enabled on two ports giving a 2Gb connection

I am new to the Freenas scene so read a few threads and decided to try it myself.
The items listed above are those used in my home Lab setup
The results so far from Freenas have been what I expected about 110MB/second.
What is confusing me is that people have been saying they get 300-400MB/second.
How on earth is that possible when a gig link can't support and I don't believe for a minute they are on a 10GB network?

When I come to create a ZFS volume it asks me about what type of Raid set I want
I choose RaidZ2 and select all my 7x 4TB disk drives but it complains this is not optimal performance. It appears it wants me to choose RaidZ3 but this looses me too much disk space. What is the issue with RaidZ2 with 7x 4TB drives is there really a performance issue?

I noticed you can create a SSD cache for Freenas what exactly is this for what advantages will it gain me over the transfer speeds I already get?

If the SSDs fail with the cache and log setup on them later on what happens then does it cause major issues?

I want to eventually setup AES encryption as my processors supports it but what's anyone's recommendation with doing ISCSI with about 10 targets on Freenas with encrypted ZFS is this doable?

 

[zambanini]

http://forums.freenas.org/index.php?forums/new-to-freenas.5/

read it. understand it. if you do not... re read the posts.

people like cyberjock put much time in writing documentation and noob guides, use them.

if you want speed an or reliability you need to understand the system. all of your questions are answered in the noob guidelines.

 

[Rayworth]

I followed your link but had been to this section before
Lots of discussions nothing specific to what I am asking
To me quite frank if this is your approach to people asking questions don't bother responding to mine. All I am after is someone's experience and guidance.
I have spent quite a while googling the answers to my questions but have come full circle and still am not a 100% sure

 

[gpsguy]

You can create non-optimal volumes, by selecting the "manual setup" button on the ZFS Volume Manager page.

That being said, if your use case is iSCSI, you'd probably be better off with a stripe of mirrors.

When I come to create a ZFS volume it asks me about what type of Raid set I want I choose RaidZ2 and select all my 7x 4TB disk drives but it complains this is not optimal performance. It appears it wants me to choose RaidZ3 but this looses me too much disk space.

btw, there are some users on the forum (including Cyberjock), who have 10Gb ethernet.

I can't address your other questions - gotta get to work.

 

[Rand]

What is confusing me is that people have been saying they get 300-400MB/second.
How on earth is that possible when a gig link can't support and I don't believe for a minute they are on a 10GB network?

Well they/we are;) Its not so expensive any more.

I noticed you can create a SSD cache for Freenas what exactly is this for what advantages will it gain me over the transfer speeds I already get?
If the SSDs fail with the cache and log setup on them later on what happens then does it cause major issues?

No advantages if your array is fast enough and u r limited to 1GBE. Some advantages if your array cant deliver. Memory sure can;) (eg if 2 clients both need a lot of small files then a Z2 array will be hard pressed to deliver. Memory can saturate the links easily. But that doesnt mean you need an SSD as L2Arc. Memory will be used as "Cache" as well.)
And failure is not catastrophic any more in most cases but still may corrupt write operations, thats why mirroring is still recommended for ZIL (or write cache as you would say which is plain wrong as its not woring that way).

I want to eventually setup AES encryption as my processors supports it but what's anyone's recommendation with doing ISCSI with about 10 targets on Freenas with encrypted ZFS is this doable?

What kind of answer do you expect? It depends of course :)
Concurrent access, same or dfifferent files, read or write, large or small size, sync or async...

 

[Dennis.kulmosen]

Yes we do have 10GBe. I am getting about 700MB/s read/write on a Mac Pro with a bit of tweaking in sysctl.
But yes read Cyberjock's guide, dont be mislead by the title, even experienced users can learn from it because often you tend to forget some of the basic guidelines.

 

[jamiejunk]

This guy has some good info on his blog as well.
http://nex7.blogspot.com/