[mythtv-users] OT: Hybrid drives in a RAID?

[Mark Perkins]

> On 20 Aug 2014, at 11:17 pm, "Matt Emmott" <memmott at gmail.com> wrote:
> 
> There's a deal on slickdeals.net this morning where one can buy a 4TB Seagate "Hybrid drive" (model ST4000DX001) for somewhere in the neighborhood of $150 shipped. This drive has 8GB of NAND flash built in, and from what I've read performs block-level offload of the frequently accessed data to the flash, giving it (in theory) a performance boost similar to SSD.
> 
> I'm planning on building a 6-disk RAID6 array in my shiny used Poweredge once it shows up. If hybrid disks offer a speed boost at an affordable price, it seems like a no-brainer to use them for my array. However, I can't find any solid information on using them in a RAID5 or RAID 6 setup. I did find this quote from HP via http://h10025.www1.hp.com/ewfrf/wc/document?docname=c03821563&cc=us&dlc=en&lc=en :
> 
> >An SSHD in RAID 0, as compared to a single drive configuration, delivers performances as >much as 70% higher.
> >Because current drives are not designed for multi-drive vibrations, they have not been tested >with RAID 5, 6, or 10, and are not recommended.
> 
> I'm going to ignore the last part about multi-drive vibrations because I assume it's some CYA warranty fluff, and danger is my middle name. But, I don't know what I don't know so I'm asking the smart people on this list if they think a hybrid drive would be a benefit, or a deterrent, or something else when running it in a RAID5 or 6 setup.
> 
> Thoughts? Thanks in advance.
> 
> Thanks,
> Matt
> 
> _______________________________________________
> 

I'm not sure I see the point of a hybrid drive like this unless you run an OS on it. After all in a media server NAS situation what is it going to cache? Play the same recording over and over again? My understanding is it's sustained read / write speeds will be the same as a standard mechanical drive. Though I guess it depends what function your NAS is going to provide, you could have any number of different functions in mind beyond just recordings and media files.

If the price was the same either way I guess why not (big 'if' though)? Maybe just more to go wrong? I wonder what their reliability is like?

I just can't see that you are likely to see any genuine performance boost in a standard media server NAS situation over a standard mechanical drive.
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