2 x SAS Expanders... is it better to divide my drives between them?

[Fr Jonah]

I recently acquired another SAS expander (basically for free...) that daisy chains to my existing expander and have confirmed that FreeNAS can see drives from both SAS expanders in my current configuration. The new SAS expander came with 4x1tb enterprise (Seagate/Dell) drives, which brings the total count of NAS dedicated drives to 8, all of which are 1TB capacity. I am seeking advice/insight into the following questions:

1. Are there any advantages to using both SAS expanders with only 4 drives each, or will performance be the same with more power consumption?

2. Should I just get rid of the SAS expander since the 1TB storage to 1GB RAM rule will likely preclude the need to ever go above 16 drives? (I am in the process of upgrading to 32GB of RAM on the c1000).

My default plan is to put all drives in one expander until I need more room, which may not happen, since I'll likely be investing in drives above 1TB capacity in the future, meaning I could easily get to 32TB of storage by adding 8x3TB drives from here on out. The obvious thought is that heat buildup would be less by diving the drives across 2 expanders.

Thoughts?

 

[Ericloewe]

Daisy-chaining expanders gains you nothing beyond the additional ports, in exchange for some additional power consumption and latency (probably negligible).

Also, the 1GB of RAM per 1TB of HDD rule is a bit more flexible once you have a decent amount. 32GB should be enough for somewhat more storage, depending on what the server is being used for.

 

[Fr Jonah]

Ericlowe,

Thanks for the response: that makes sense. In that case, I'll plan on holding onto the 2nd expander until we need the space... at least forestalls any future concerns about getting ahold of a compatible unit when the time comes. I'll install it in the server rack but not turn it on or connect the SAS cable until it's necessary.

Our usage case is mainly storing ultra high resolution images for printing... file sizes up to 6GB or so per file. Not much traffic other than when we're doing layouts, etc. In your experience, what would be a reasonable amount of storage to max out our unit assuming 32GB RAM? Perhaps 40TB or so?

Thanks!

 

[cyberjock]

6GB for a single image!
If you have one of the grand canyon I'd like one. :D I grew up there and I miss it. :*(

If you are just throwing the image on there and then not really using it again except occasionally, and if that's how all of your data is going to be stored on your server you could probably go to 50-75TB. It's really tough to set a line, but when the zpool starts performing like crap, you know its time for more RAM. ;)

 

[Fr Jonah]

cyberjock: Thank you for the response. The Grand Canyon is amazing but, alas, we don't have any gigapixel images of said canyon. Our file sizes get so large because we store a lot of layered large format Photoshop files (psb) with print dimensions as large as 150" vertical at 300 dpi. It starts adding up quick :)

I have another thread on the storage forum I was hoping you would chime in on as I know that, at one time, your pool consisted of two 8 disk vdevs (with 1TB and 1.5TB drives on each vdev). I was thinking of setting up my pool similarly since I have 8x1TB drives, but the "non optimal configuration" warning from FreeNAS gave me 2nd thoughts. Am I really going to lose much by doing an 8x1x1TB configuration vs. one of the geometric configurations? What's your experience with this?

 

[cyberjock]

Got a link to that thread? I can take a look...

 

[Fr Jonah]

Sure do! Thanks!
http://forums.freenas.org/index.php...drives-and-could-use-some-setup-advice.21268/

 

[cyberjock]

Posted in that thread. ;)