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Anyone here use NAS (Network Accessible Storage) devices?

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lilshawn:
from what i understand ZFS is a real memory hog. if I stuck with straight UFS I wouldn't have an issue.

apparently it's something like this...

right off the bat ZFS leaves 1GB of RAM available to the OS automatically. That means the ZFS is assuming control of the remaining 1GB of my RAM right now. ZFS will use all the RAM you give it to try and improve performance...what happens if it needs more is unknown at this point, i would assume performance degradation, but i'm guessing I get what I had last night and the thing crashes.

copy paste from some other info on ZFS memory requirements... which sounds like ~2GB per TB of disk space.


--- Code: ---1) Read cache. This function is known as ARC. Estimate this at about 1 GB per TB of zpool.
2) Temporary Write cache. Incoming writes queue up here before being added to the ZFS Intent Log (ZIL), and then ultimately to the live filesystem. This is generally only 200-500 MB, but estimate at least 1 GB.
3) Checksums: ZFS performs checksumming on all blocks of data stored within the zpool, and those checksums have to be calculated and verified for each read and write. These operations use considerable CPU and RAM. Difficult to estimate.
4) Parity-Data: If your drives are in a RAID-Z configuration, then ZFS uses RAM during the calculation of Parity Data which allows the fault-tolerance offered by RAID-Z. Calculating parity data uses considerable CPU and RAM, and must be done in addition to the standard checksum operations. Difficult to estimate.

--- End code ---

ChadTower:

Same idea as the discs in a DVR but for a different usage reason.  They fail faster because they get worked much harder.

drventure:

--- Quote from: ChadTower on April 25, 2013, 09:05:19 am ---Same idea as the discs in a DVR but for a different usage reason.  They fail faster because they get worked much harder.

--- End quote ---

Definitely. If you're picking a drive for a DVR, you generally want one that's going to run cool. That usually means a 5000rpm drive vs the faster (but hotter) 7200rpm drives.

I know WD makes some large, slower speed drives specifically for DVR uses because they run quieter and cooler. I used one when I upgraded my Tivo HD. Haven't has a single issue in several years, and it's reading or writing almost continuously.

kahlid74:
Don't forget that real raid drives often times used different epoxies that have a longer shelf life.  This translates to better life overall as they sustain hotter/faster speeds for prolonged periods of time without negative results.

Again, get whatever disks you like, BUT SPEND THE MONEY to have a backup solution.  If you can't lose the data, B A C K IT UP!

lilshawn:
a quick update...just for prosperity's sake, and as a note to anyone else who decides to attempt this as well...

i went ahead and popped in the extra 2gb ram (for 4gb total) and have had no problems at all.

this file system is pretty memory hungry. It's all in the name of reliability and performance, which is okay, but neither of which i really have interest in at this moment. It's basically that would be geared towards the corporate users...but it's a good learning exercise anyways. It's really only because I striped the 2-500gb drives together using ZFS to get a terabyte for testing. in actual practice, when i get a couple of 2tb drives, i think i'll go straight ufs and just do a simple dupe backup on it. that should reduce the memory footprint quite a bit that I could probably drop back to 2gb again. It's in there so i won't bother. I don't really need the performance and safety and checking of the ZFS since i'm just serving video off it. It's not imperative that data be available instantly.

but, so far so good.

 :cheers:

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