FreeNAS questions

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Cadet
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Jan 25, 2014
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Hi,

This is my first attempt to check FreeNAS+ZFS+iSCSI.

Everything was performed in VMWare Workstation. FreeNAS was configured as it follows:

2 cores of 3770K
8GB RAM out of 32GB
8x 3GB virtual disks stored on a Samsung 840 PRO 512GB SSD (500mb/s+ write/read)

I've created a 3GB zvol(if I remember correctly, this was the maximum possible?!) on a RAIDZ2 ZFS Volume.

iSCSI was configured according to the following guide:
View: http://www.youtube.com/watch?v=7jn2q2ysr5g



The transfer speeds were not astonishing ranging from 7mb/s to ~60mb/s, but it felt quite snappy when trying to display thumbnails of photos, probably due to the low access time of the SSD.

I have some questions:

-where do i see how much space do I have left for adding new zvols?

-how do I see if everything has been written to the array? (when transferring via iSCSI)

-where do I see if everything is ok with my volume?

-where are the checksum settings?(where can I read more about them)

-how do I see the volume type raidz2 z1, etc?

-how much space does ZFS take on a 8 HDD raidz2 config, on each hdd?
(I could not create a new volume/zvol on my 8x3GB configuration, due to lack of space, where's the remaining space?)
 

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Michael Wulff Nielsen

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Oct 3, 2013
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First you should be aware that Freenas was not meant to run in a vm. It is an unsupported configuration.

Zfs itself does not occupy a lot of diskspace on the disks. As for the rest of your questions I believe you will find answers in the freenas manual.
 

gpsguy

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Jan 22, 2012
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3Gb virtual disks are too small for testing. When setting up a ZFS pool via the GUI (highly recommended), it allocates a 2Gb swap file on every disk.

Do a "gpart show" from the console, to see the partitions on your virtual hard disks.
 

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Cadet
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Jan 25, 2014
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First you should be aware that Freenas was not meant to run in a vm. It is an unsupported configuration.

Zfs itself does not occupy a lot of diskspace on the disks. As for the rest of your questions I believe you will find answers in the freenas manual.


Before getting to the real thing, you have to perform some tests. I don't know about others, but I cannot afford to buy hardware of ~2000 euro, and afterwards to discover that I have some compatibility issues with UTF-16LE filenames when using CIFS+ZFS, for example.

It really makes sense to to do a test like I did. Just to see if I'm able to configure the basics of FreeNAS, and to be sure that I can actually enable the share.
 

cyberjock

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Mar 25, 2012
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Michael isn't saying you shouldn't ever run it in a VM. But trying to do VM testing and actually using the performance results in a VM to determine if you are happy with the performance of a real FreeNAS system is hogwash.

VMs are great for learning the OS and how to do things in the OS. It will ALWAYS suck in the performance arena. It will ALWAYS suck in the reliability arena. Anyone trying to complain about performance or reliability of FreeNAS in a VM lacks the basics to realize that what you are doing isn't and wasn't meant to be fast or reliable. It was meant to allow you to see if you like FreeNAS before buying hardware.

Your performance-related questions are invalid solely based on your questions being from a VM.
 

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Cadet
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Jan 25, 2014
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cyberjock, you are right.

Since you mentioned performance. Let's say I take an 2.7-3Ghz AMD Athlon II CPU, with 16GB of RAM and 8x3TB Toshiba 7200RPM, RAIDZ2 ZFS volume, iSCSI+NTFS acess, no compression, no deduplication, no encryption.

What can I expect? Can I expect steady 80MB/s with large file transfers?
 

Michael Wulff Nielsen

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The reply would be probably. But it all depends. Many AMD systems ship with crappy realtek nics that limit performance a lot. So the answers is: "it depends".

Also don't forget ECC memory, it has little impact on performance but a lot of impact on system reliability.
 

expansion

Cadet
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Jan 25, 2014
Messages
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Yes, ECC, I forgot to mention. There's no point in using ZFS without ECC RAM, I'd risk getting everything corrupted.

I need to read some more about checksums(in the manual there are 6 occurences of the word checksum, and I've found that it's 256bits long), and about the extra space that ZFS takes for each MB/GB/TB occupied with data. Any suggestions where to read about this?

How many bits can it correct with the checksum?


iSCSI+NTFS vs CIFS?
I don't need concurent access, it will be only one computer, running Windows 7. I'm still thinking about which path to choose.

There will be lots of small files along with large files, there will be searches through those files.

Can you point out some advantages/disadvantages between iSCSI+NTFS vs CIFS?

1) I'm worried about the fact that with iSCSI+NTFS, ZFS will be "dumb" not aware of what is stores in those blocks. Also, risks full volume of corruption due to possible crashes of the Windows machine? Could it be possible?
2) I'm worried about the fact that with CIFS, there could be certain features that NTFS could have and couldn't have with CIFS.

I don't have much experience, so that's why I'm asking.
 

cyberjock

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iSCSI will always be slower than doing things with CIFS(assuming you don't have a crap processor). iSCSI adds latency and needs more RAM to stay high performing.

And if you are worried about "certain features" why not see if "those features" are available in FreeNAS. Heck, create a FreeNAS VM and see for yourself first hand! No need to even ask questions then.
 

Dusan

Guru
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Jan 29, 2013
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I need to read some more about checksums(in the manual there are 6 occurences of the word checksum, and I've found that it's 256bits long), and about the extra space that ZFS takes for each MB/GB/TB occupied with data. Any suggestions where to read about this?

How many bits can it correct with the checksum?
None. The checksum is just that, a checksum, not an error correcting code. It allows the system to detect data corruptions. To fix them you need to setup your vdevs with some redundancy (mirror, any of the RAIDZs, or the copies zfs property). For more information see: https://blogs.oracle.com/bonwick/entry/zfs_end_to_end_data
 
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