Finished a project and got to run a test tonight.

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NightShade

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So I put together a FreeNAS box since I had some not too old drives crash and die while taking the data with them and wanted something better for serving files as well as to handle my Plex. Tonight when I decided to do a review on some drives I did a simple speed test. Basically I created a dataset(think folder) that did not have compression turned on to skew the results. I then told the system to tell me how long it took to write a hefty file. For the non geeks feel free to skip down to the explanation:

dd if=/dev/zero of=testfile bs=1024000 count=50000
50000+0 records in
50000+0 records out
51200000000 bytes transferred in 95.467597 secs (536307623 bytes/sec)
dd if=testfile of=/dev/zero bs=1024000 count=50000
50000+0 records in
50000+0 records out
51200000000 bytes transferred in 59.494667 secs (860581335 bytes/sec)


Explanation
That is a 47.68GB file (basically an entire BluRay Disc) written in 95.467597 seconds and read in 59.494667 seconds. In other terms write at 511.462805748MB/s and read at 820.714316368MB/s. That is SSD speeds and better from spinning hard drives and once you get to a certain file size on an SSD it will slow down since it takes longer to write to multiple depth cells and most SSD's that consumers buy are not SLC or SingleLevelCell drives. My Plex is very happy living there.:hyper:

It is 7 drives that are 7200RPM in a ZFS raidZ3. Basically the pool of drives act as one big drive with the total capacity of around 4 drives with a fault tolerance of 3 failures. What actually slows down the speeds is the fault tolerance writes since much more data has to be written than it takes to read the same file.

Like most of my projects this has been a few years in the making. I buy a part here and a part here and pay it off as I can with a lot of used parts. In fact the only thing that was brand new was the drives. A good portion was Ebay used stuff and the rest were refurbished and/or open box. Nearly everything either had a rebate or some sort of cash back program with the drives being on sale.

Now who wants to watch a movie
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tRidiot

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I agree, I understood it and think it's cool as heck. Also in for the explanation as to the RAID structure.


Some things I found on Wikipedia:

"ZFS stores the checksum of each block in its parent block pointer so the entire pool self-validates."

"RAID-Z does not require any special hardware: it does not need NVRAM for reliability, and it does not need write buffering for good performance. With RAID-Z, ZFS provides fast, reliable storage using cheap, commodity disks."

"There are three different RAID-Z modes: RAID-Z1 (similar to RAID 5, allows one disk to fail), RAID-Z2 (similar to RAID 6, allows two disks to fail), and RAID-Z3 (allows three disks to fail). The need for RAID-Z3 arose recently because RAID configurations with future disks (say, 6–10 TB) may take a long time to repair, the worst case being weeks. During those weeks, the rest of the disks in the RAID are stressed more because of the additional intensive repair process and might subsequently fail, too. By using RAID-Z3, the risk involved with disk replacement is reduced."


So these things have something to do with it? Are you really concerned with having that many drive failures? What kind data are you storing that it takes that kind of redundancy and self-healing file restoration and on-the-fly continuous rechecking? It sounds like you've got movies on there, is this mainly for a home NAS setup?

I've got a 12TB 4-disk NAS in RAID5 which has about half of its 8 or so terabytes of accessible storage full right now, but nothing is critical data - it's used strictly as a home media server for Kodi. I'm wondering if this kind of setup (I'd never researched ZFS before) would be of any benefit to me. I believe I'd need to overwrite/flash my storage device's hardware RAID in order to use another device to perform the actual read/write, yes? I mean, I couldn't use my Netgear NAS, I suppose I'd have to build a separate box like you did? What did you build for your box? It's not RAM-intensive per Wikipedia, as there's no write-caching?

I may not be understanding everything completely, I'm pretty shallow in this gene pool...

Cool writeup, though, thanks!
 

761mph

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so..............................in redneck language, you built a tractor with several BIG motors ?.......like this....

only it's a computer
 

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Commander Keen

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so..............................in redneck language, you built a tractor with several BIG motors ?.......like this....

only it's a computer
Basically. Although it would have multiple fuel tanks (for capacity) in addition to more motors (speed/performance.

All set up so that a failure of one disk (engine/fuel tank combo) doesn't bring the whole thing crashing down.
 

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