Does anyone have any rule of thumb for whether or not it's worth paying the extra cost of 7200 RPM drives these days?  It seems most standard NAS drives are 5400/5900 RPM and most enterprise editions are 7200.

 

I can't imagine this makes any difference for normal read/write or even parity check speeds, but what about having multiple full bit rate HD video files streamed simultaneously from the same physical drive?  Does anyone have any rule of thumb or have done any testing on how many you can pull from the same drive before it can't keep up with the seeking back and forth?  It would seem the 7200 RPM drive would do better in that environment but if the 5X00 Drive can handle 4 or 5 streams, I can't imagine I'd ever care.

 

Most of my videos are H264 encoded with handbrake, but having the original uncompressed DTS-HD / Dolby TrueHD / PCM audio.  

 

Any thoughts are appreciated.

 

 

 

It would only make sense in the parity drive to invest in high RPM. In the situation when you have multiple writes simultaneously.

For reading operations, even multiple concurrent, the first bottleneck will be your GB NIC not your HD.  One decent 5400 RPM disk is enough to saturate one GB NIC.  So unless you look at uprating your LAN to 10 GB ethernet, not worth in investing in 7900 RPM spinners.

 

 

1 hour ago, zonderling said:

It would only make sense in the parity drive to invest in high RPM. In the situation when you have multiple writes simultaneously.

For reading operations, even multiple concurrent, the first bottleneck will be your GB NIC not your HD.  One decent 5400 RPM disk is enough to saturate one GB NIC.  So unless you look at uprating your LAN to 10 GB ethernet, not worth in investing in 7900 RPM spinners.

 

 

 

Thanks!

RPM is only one dimension of drive performance. The other is data density. A drive with more data packed into each track is going to read more data in a revolution.

 

If you compare a 5400 RPM 8T drive vs a 7200 RPM 4T drive, you'll find the higher density of the 8T results in faster performance when reading data sequentially (which is the norm for most unRaid arrays). The slower RPM can slow down 'normal" unRaid writes, which require both parity and the drive being written to each make a full rotation.

 

Normal writes will never be faster than parity..So investing in data drives faster than parity will not improve write speed. If parity is involved in two separate write transactions at once, write performance is seriously impacted. Better to do them serially. But sometimes you can't control that, and a little extra juice in the parity drive can help. If parity is fast and a data disk is fast, writes to that drive are faster, unaffected by other data drives that are slower..So if you have a fast parity, one or two fast data drives for the disks you write to most is helpful. (Not trying to get anyone over excited, write performance will only be slightly better).

 

If your goal is fast turbo (reconstruct) write performance, the slowest disk in the array will be the gate. So unless all the array drives are fast, having one or two fast ones means nothing. But overall, even slow turbo writes are going to generally be much faster than normal writes. (Of course.your drives are spinning a lot more, and while a write is happening, read performance on every other disk in the array is negatively.impacted.)

 

I doubt that playing movies, even high bit rate, is going you over tax. Think about a 30G media file that takes 2 hours to play. It is playing back at 1/24th of the speed your drive is able to serve that file (assuming 100 MB/sec). You'd be able to play bank several of those without a problem!