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Simulating Raid 10


DrToast
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I've been trying to decide on what to do with an old Windows 10 PC and I think I've settled on making it a file server using DrivePool. 

I had considered building a RAID machine using one of the various solutions, but I like the idea of having a backup Windows machine available. 

I realize that DrivePool is not RAID software, but it does have many features that are similar. What I'd like to try to do it attempt to simulate a RAID 10 setup as much as possible. 

I'm going to start with four 8 TB hard drives and then add in pairs as needed. I have two old 500 GB SATA SSDs that I can use for caching, but I'm wondering if that is going to be enough. I will be running the server on a 2.5Gbe network. I'd like to be able to saturate that connection, which I think I will be able to do with SSD cache and full duplication. 

Am I on the right track? Is there anything else I should consider? 

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I am trying to wrap my head around your idea. DrivePool works differently than RAID, but I think I can offer some suggestions.

See the source image

Since DrivePool writes full files to one disk at a time, not packets spread over multiple disks, would not standard duplication in DrivePool give you the same result of having a copy of your data on two separate disks?

Essentially, Raid 1+0 is Mirroring with Striping combined. Mirroring for data redundancy, and Striping for speed in a packet writing system. I think you could do something similar in DrivePool using Duplication (Mirroring) on either your entire DrivePool, or just selected important folders, and using 2 SSD's, one each as frontend cache for each duplicate file (Striping) for increased speed. I was able to achieve RAID-like speed on my DrivePool when I added an SSD frontend cache (for WRITES). I also set my DrivePool SSD cache high enough that I can also use it as a very fast READ/WRITE cache for temporary files. I set my SSD cache not to flush until it has 100GB. That's more than I need on any of my temporary working directories.

Another big plus with using DrivePool is that you don't have to add additional HDDs in pairs. I recently built a DrivePool with 3 end-of-life HDDs that I cannot trust on my main DrivePool. I set that entire end-of-life DrivePool to 2X Duplication, In theory, if/when any one drive fails, I'll still have another copy of my files on one of the other 2 remaining HDDs. If there is enough capacity on the remaining 2 HDDs on that DrivePool, it will duplicate the files as needed that were on the failed third HDD. I would never consider using those end-of-life HDDs in a RAID system, but DrivePool lets me get more time out of those old drives. That saves me money and was worth the cost of DrivePool itself.

Another consideration is that a typical RAID system, with packet writing across disks, leaves you with nothing if a HDD fails - unless you build in duplication like your RAID 1+0 setup. You can't read a failed RAID HDD. DrivePool, on the other hand, can often retrieve many, if not most, files off a failing HDD because it contains the entire file, not mere packets. I have been able to retrieve all but maybe 2 or 3 files off a 4TB HDD that crapped out on me. Unless the HDD is totally dead, you have a decent chance of retrieving files off that failing HDD.

Bottom line: To replicate the features of RAID 1+0, use Duplication on your DrivePool for redundancy and add 2 SSDs as frontend cache, one SSD for each duplicate file to be written for RAID-like speed. When you want to expand your setup, in DrivePool you can add one disk at a time instead of having to add disks in pairs.

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