Disk Space ZFS

[Snufkin]

I have just setup FreeNAS on a system with 4 x 2TB disks and I want to use RAIDZ1 and iSCSI. Reason for RAIDZ1 is that I want a bit more disk space than what you will get with a RAID10 volume.

I followed the wizard and at some point it asks me for the space of the iSCSI volume. When setting up the volume it estimated the size at 5.5TB. I want to use the maximum available space for the volume if however I specify 5.5TB and look at the Storage it seems that the Maximum size is 5.1TB. (Please see attached image)

I ran the wizard a few times and found that I can, for instance, specify the size for iSCSI at 7TB ... but what will happen with such a config ?

Further if I do it manually it indicates that I cannot create the volume bigger than 80% of the available space. In other words 4 TB on my RaidZ1 setup.

So what would be the correct configuration for maximum disk space with my current setup?

 

[depasseg]

There is a difference between TiB and TB. Also, Bidule0hm has a great sizing calculator.

Finally, performance on iSCSI really starts to suffer beyond ~50% full, and out past 80-90% it's probably really bad. Jgreco has a couple graphs that depict it.

You might want to reconsider your approach. Either avoid iSCSI, add storage, or plan on a lot of waiting.

 

[Snufkin]

Ok ... And lets say that I still wish to use iSCSI ...must I specify the disk space as 5.1TiB ? In the wizard you can just us T Is this TB or TiB ?

 

[depasseg]

This is covered in the manual.
http://doc.freenas.org/9.3/freenas_storage.html#create-zvol

 

[Mirfster]

I ran the wizard a few times and found that I can, for instance, specify the size for iSCSI at 7TB ... but what will happen with such a config ?

I have seen some mention of this somewhere, but have not used it. I believe that it is considered "over-provisioning" or something similar. Basically, it is like taking a loan/mortgage with the "promise" that you will actually provide that space before you get to catastrophic levels. While I am not 100% sure, that is my take on it. /Was trying to think of an example dealing with stocks, but coffee has not kicked in yet...

I have just setup FreeNAS on a system with 4 x 2TB disks and I want to use RAIDZ1 and iSCSI

I think that the normal suggestion around here is to use mirrored vdevs for iSCSI and not RaidZ1...

Lastly, you never provided your specs and running iSCSI requires a lot more resources: Why iSCSI often requires more resources for the same result
Excerpt from linked thread:

What people want -> old repurposed 486 with 32MB RAM and a dozen cheap SATA disks in RAIDZ2

What people need -> E5-1637v3 with 128GB RAM and a dozen decent SATA disks, mirrored

 

[Snufkin]

The computer is a HP ML 110 G7 14GB RAM and Xeon E312220 3.1Ghz CPU

 

[Mirfster]

14GB RAM

You are gonna be hurting trying to run iSCSI with that... :(

 

[Snufkin]

So what will you recommend with the specs I have given you ? CIFS with RAIDZ1 ? Will that work better ?

 

[depasseg]

Will CIFS work for your needs? That's quite a shift to go from iSCSI (raw block device) to CIFS (file share).

 

[Mirfster]

So what will you recommend with the specs I have given you ? CIFS with RAIDZ1 ? Will that work better ?

It would really depend on your "use-case"... If it is for simple file sharing, etc.; then what you have should work fine. I still suggest bumping up the RAM, but again it depends.

I personally am a fan of RaidZ2, but there always is the decision to be made between Space, Speed and Redundancy (each has their pros and cons).

Is there a particular reason you were looking at iSCSI to begin with?

Side Note: I did not check your actual specs, but since you are running a Xeon E312220, I am assuming you have ECC RAM. If not, then you need to get it. ;)

 

[Snufkin]

It doesn't have to be iSCSI to work ... It will be used to store backups and ISO files.

 

[Mirfster]

It doesn't have to be iSCSI to work ... It will be used to store backups and ISO files.

Ahh, then CIFS is certainly much better for this over iSCSI...

 

[gpsguy]

Use CIFS instead.

It doesn't have to be iSCSI to work ... It will be used to store backups and ISO files.

 

[pirateghost]

It doesn't have to be iSCSI to work ... It will be used to store backups and ISO files.

Why would you be looking at iSCSI for this? Iscsi would require another system to provision and format the 'disk'. Seems a huge waste when hosting and sharing files is what freenas excels at....

 

[jgreco]

14GB RAM

How did you manage THAT?

 

[Ericloewe]

How did you manage THAT?

8+4+2?
4+4+4+2?
8+4+1+1?

Don't know how one would realistically arrive at those combinations, though. Maybe standard 6GB upgraded to 14GB?