Different HD speeds/cache/manufacturer in Raid 5

[nextJin]

Imagine a scenario in which someone (friend of mine wanting a htpc similar to my sig) had 6 hard drives each of which are different than the next.

He has 6 hard drives 2TB each from WD Greens to Samsungs to Hitachi, 7200 to 5400 rpm, 32-64mb cache, etc

What concerns should I have before going down there and building this thing for him?

Should I just assign different HDs to separate areas for TV Shows, Movies, DVR, and Games?

 

[dawp]

Ideally, you want matching drives for a raid 5, not sure you can do a raid 5 with non-matching drives, tho it's been over 15 years since I've had worked with any raid setups.

unless you go jbod, your best bet is to assign each drive to a different function.

 

[imagoon]

You can do RAID 5 with those disks but the performance will be... unpredictable at best. Performance would typically be closer to the performance of the slowest disk drive. If you are concerned about data loss then use some of them to back up the others. If you are interested in capacity, the do JBOD and backup religiously. If you are using Windows you can mount the drives to directories in disk manager, in Linux you would just mount them where ever.

 

[nextJin]

You can do RAID 5 with those disks but the performance will be... unpredictable at best. Performance would typically be closer to the performance of the slowest disk drive. If you are concerned about data loss then use some of them to back up the others. If you are interested in capacity, the do JBOD and backup religiously. If you are using Windows you can mount the drives to directories in disk manager, in Linux you would just mount them where ever.

Performance is not really a concern, it would be specifically for some type of redundency. I know from experience losing 4+ TBs of video backups was a huge PITA for me. Right now all I worry about is one drive dying, I can't afford to buy 12 TB's of backup for videos. I would imagine it would be the same for him but in his case he already had these things laying around.

When you say unpredictable do you mean some sort of failure or purely on performance? His WD Green drive is a concern, unless it is an older model. If my history serves me correctly they don't play well with Raid.

 

[imagoon]

I mean unpredictable in performance and reliability. You could find drives getting booted regularly if the performance of one is far off of another (ie say a 4k drive not being aligned and the green drive sleeping, data may not return in time for the controller to not panic.) Also RAID isn't a backup, you should not really expect it to be so. RAID 5 should survive a drive failure but it is harder to predict the end result when the drives are a mismash of stuff. ZFS and ReFS with Storage pools is supposed to be more resilient to this issue and was designed with the "mix of drives" approach.

 

[Old Hippie]

AFAIK the array will take the lowest characteristic of any parameter (size, speed, cache) of any of the drives in the array.

And green drives are not for RAID.

 

[Ferzerp]

Consumer drives + parity raid = asking for trouble

 

[Anteaus]

Should I just assign different HDs to separate areas for TV Shows, Movies, DVR, and Games?

That's what I would do.

As mentioned earlier, it's not a good idea to run raid 5 with consumer drives. I'm not going to go into detail here, but there are plenty of good sources out there if your curious.

If your looking to build a file server for archival purposes, then that is a different path. For what your doing I think just running JBOD is the best way to go. It keeps things simple and lets you use each drive to maximum potential.

As a side bar, Raid 5 is not a substitute for a proper backup so whichever route you choose I would maintain a seperate backup of all of the media unless you don't mind losing it.