UFS and RAID0, RAID1 or RAID3

[OldDude]

I appreciate that in an ideal world we'd all be taking advantage of the benefits of ZFS, but in some cases there are those of us that need to use a UFS system.

Unfortunately while the documentation for FreeNAS states that it is capable of supporting UFS and RAID0, 1 or 3, there is absolutely no description anywhere on how to configure a system that way.

I have a situation at work that has proven that a ZFS based configuration will not work in the company's manufacturing environment, so I'm having to "downgrade" the configuration to use a UFS formatted system. However, nothing in the documentation explains how to go about configuring a UFS system with any of the supposedly supported RAID formats. All the focus is on working in a ZFS environment.

Searching through the forums, I can see that I am not the only person looking for this information. Can someone step up to the plate and provide the necessary details on how to go about this?

While it may not be the defining reason why someone would choose to use FreeNAS, since FreeNAS supports UFS and RAID 0,1 and 3 it should ensure that the documentation describes how to achieve this setup.

 

[cyberjock]

I could be wrong, but isn't the main difference that you click the radio button for "UFS" instead of "ZFS" when setting up the volume?

 

[ProtoSD]

I think it can only be done from the command line. I don't know the incantation though ;)

Probably looking at FreeBSD docs on the topic would shed some light.

 

[peterh]

Have a loog at the freebsd handbook, the chapter about geom ( the new disk layer )
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom.html

 

[William Grzybowski]

It is as simple as select UFS for filesystem and then choose 2 or more disks... you'll be given the option to do mirror (raid 1), stripe (raid 0), or raid-3.

 

[OldDude]

It is as simple as select UFS for filesystem and then choose 2 or more disks... you'll be given the option to do mirror (raid 1), stripe (raid 0), or raid-3.

If you select 4 Drives... you do not get the opportunity to select RAID3.

I have 4 3TB drives.

If I select all 4 I can either choose RAID0 which generates 4 identical drives and an array of 2.7T in size. Redundant? Yes.... Efficient? Hardly.

The only other option is RAID1, which produces an array of 10.7T with absolutely no redundancy, so for all intents and purposes it is merely a striped JBOD .

Where is RAID3 for 4 drives? Y'know, the typical 1 Parity drive and the remaining drives striped as a data array. RAID3 requires a MINIMUM of 3 drives, but the implementation of RAID3 with the FreeNAS system works only with a 3-drive system.

Since there is no ability to set up RAID5 or RAID10 the only recoverable RAID configurations for a UFS setup appear to be for 2-drive or 3-drive systems. This is somewhat disappointing.

I would much prefer to work with the ZFS configuration, but as I mentioned before I have certain applications being used in the company which have issues with the way it doesn't handle some extended file attributes generated by Windows apps. This is forcing the UFS route, but the lack of a redundant RAID configuration for a larger array really is forcing me to look at alternative solutions which I really didn't want to do.

 

[William Grzybowski]

Of course not! The number of components for raid3 must be equal to 3, 5, 9, 17, etc. (2^n + 1).

 

[OldDude]

Of course not! The number of components for raid3 must be equal to 3, 5, 9, 17, etc. (2^n + 1).

Your definition of RAID 3 does not match up with definitions defined by many others.

RAID 3 requires a minimum of 2 Data Drives which are Byte-striped and a 3rd Parity drive to hold the parity checksums of the Data drives.

Older specifications also dictated that the drives had to operate in synchronization with one another, but that aspect seems to have been depricated.

A 4 drive RAID3 system does not require 5 drives as you assert. The 3 drives maintain the data stripe while the 4th holds the parity checksums for the array.

Check wikipedia for a simple illustration: http://en.wikipedia.org/wiki/RAID_3#RAID_3

The formula I have for RAID3 is d * (n - 1)

 

[William Grzybowski]

With all due respect, I don't care what your fomula is, I care for what the formula for the freebsd graid3 implementation is, which is (2^n + 1)

 

[OldDude]

With all due respect, I don't care what your fomula is, I care for what the formula for the freebsd graid3 implementation is, which is (2^n + 1)

Fair enough.

But given that this is listed in the noob section, what are the odds that I would have gone digging through the FreeBSD specifications to find that answer?

I have no issue with variations and interpretations of how to implement features within a product... as long as those are explained within the documentation of the product. Which brings me back full circle to my original point. The FreeNAS documentation does not provide this information.

You obviously are very well versed in the FreeBSD documentation and were able to provide the formula you quoted as if it should be a "Duh" moment for the rest of us.

My argument is that FreeNAS should not be making the same assumption and should ensure the documentation informs how the process is implemented.

 

[William Grzybowski]

So it comes the moment that I personally _LOVE_ to say: FreeNAS is an open source free product, patches are welcome, documentation is a wiki, anyone can contribute.

Arguing on a forum wont improve anything.

 

[OldDude]

So it comes the moment that I personally _LOVE_ to say: FreeNAS is an open source free product, patches are welcome, documentation is a wiki, anyone can contribute.

Arguing on a forum wont improve anything.

I'm not arguing.... but you can't seriously be suggesting that, as the noob... I be the person to fill in that gap in the documentation.

You've successfully proven that you're far more knowledgeable for this topic.

Might I politely suggest you take your own advice and contribute to the documentation?

 

[ProtoSD]

Thread closed.