FreeNAS works with Raid or Replaces it?

[gpsguy]

Look near the end of section 1.3 of the manual.

"At 90% capacity, ZFS switches from performance- to space-based optimization, which has massive performance
implications. For maximum write performance and to prevent problems with drive replacement, add more
capacity before a pool reaches 80%. If you are using iSCSI, it is recommended to not let the pool go over 50%
capacity to prevent fragmentation issues."

 

[solarisguy]

90% rule is not FreeNAS specific.

If one fully understands the resulting limitations (scrub and resilvering take significantly longer), for another ZFS implementation, Oracle suggests that pools that have minimal write activity, can have utilization up to 95%.

 

[Bidule0hm]

[...], can have utilization up to 95%.

Or how to play with fire... :D

 

[Deleted47050]

Yes, in the manual. Plus the GUI will warn you if you're over 80 % ;)

Look near the end of section 1.3 of the manual.

"At 90% capacity, ZFS switches from performance- to space-based optimization, which has massive performance
implications. For maximum write performance and to prevent problems with drive replacement, add more
capacity before a pool reaches 80%. If you are using iSCSI, it is recommended to not let the pool go over 50%
capacity to prevent fragmentation issues."

Thanks both. I tried searching for "80%" in the docs but I got no results :/

 

[Jailer]

Is this documented somewhere?

Dru did a nice write up for the members that answers a lot of questions about ZFS.
https://forums.freenas.org/index.php?threads/zfs-primer.38927/

 

[gpsguy]

The "80%" search worked for me. :)

I searched the PDF version of the documentation. You can download it, via a link in my signature.

Thanks both. I tried searching for "80%" in the docs but I got no results :/

 

[gpsguy]

That's just section 1.3 of the documentation.

Dru did a nice write up for the members that answers a lot of questions about ZFS./

 

[Deleted47050]

The "80%" search worked for me. :)

I searched the PDF version of the documentation. You can download it, via a link in my signature.

I figured as much, it doesn't work in the online version: http://doc.freenas.org/9.3/search.html?q=80%&check_keywords=yes&area=default

 

[gpsguy]

We do appreciate the fact that your tried to RTFM.

I find the PDF version easier to use. I generate a new PDF as documentation updates are made and make them available to the community.

 

[tethlah]

SO the controller suggested is a $200 controller, and with 12 drives I'll be needing 2 controllers. Aren't there any good controllers I could use for less than $200?

Here's another question, if a controller dies, since they will be set to JBOD with the OS handling the RAIDZ2, just swapping out the controller and setting it to JBOD again won't cause an issue with the OS being able to recognize the drives rigth? Or should you not set them to JBOD at all and just have the controller be a connection point with no configuration (IE, just connecting as each drive being a single entity rather than any sort of raid)

 

[SweetAndLow]

The controller is $100 on eBay and you flash it to IT mode. If you do this you can't configure any type of devices. It just turns into a dumb hba and treats the hdd as normal disks. Have you read the noob guide yet? I vote you read that before asking any more questions because we are just repeating ourselves.

 

[depasseg]

SO the controller suggested is a $200 controller, and with 12 drives I'll be needing 2 controllers. Aren't there any good controllers I could use for less than $200?

That's why most people avoid direct cabling their drives. Find an enclosure that has a backplane with a builtin expander. So then all you have to do is provide a single cable from the controller to the backplane and it shares those SATA channels across all drives.

 

[tethlah]

yeah, thats the weird part, i thought this had that until I got it, the enclosure actually has a single molex for each 4 drive cage, but 4 sata connections per cage to cater to each individual drive.

 

[tethlah]

So this is pretty much the last question until the build as I fully have everything else pretty much nailed down. Since I'm going to be using this NAS as a media server, I was thinking about getting myself a couple 32GB low profile usb ssd jump drives for the OS and also putting an instance of MYSQL on there in a JAIL (I think that's correct from what I've read). This way all the installations of XBMC in my house will have a central database to poll the library data rather than constantly trying to sync a local library.

My question is can I actually do that? Can I actually install MYSQL in a jail and have it available 24/7 along side my data and keep it on that jump drive (for the sake of not having to have my drives spun up at all times to serve out database information).

 

[danb35]

Can you put a mysql server in a jail? Sure. Will it be available 24x7? As long as the server's running, and you don't do something manually to disable it. Keep the hard drives from spinning up? Please, don't go there. It's a fool's errand. It adds wear to the hard drives, saves only minimal energy, and complicates your system setup unnecessarily. But if you must, don't put the jails on a USB stick. Put them (and the .system dataset) on a SSD pool.

 

[tethlah]

Why not just put them on the USB stick? This entire thread people have been trying to convince me to not put the OS on SSDs and just use USB. If I'm going to buy SSDs just for a mysql database, may as well just put the os on SSDs and call it a day. The point with the USB OS is to not need internal SSDs...

If I'm going to end up buying SSDs, I'm putting the OS on them too, no need to have USB and SSD drives.

 

[danb35]

Because USBs have absolutely lousy write performance and (at least sometimes) die very quickly. You hadn't previously stated a requirement to have a mysql database running on the boot device, so the extra speed and reliability of an SSD isn't really warranted.

Or put the jails on the pool and forget about trying to make your hard drives spin down.

 

[tethlah]

So from what you are saying using a USB for freenas is a bad idea anyway as they sometimes die very quickly, so the USB idea is out, I'll just get the SSDs regardless of where I put the database.

So where will the bottleneck be on sending library data to the XBMC box? The gigabyte connection, the SATA connection, or the Drive Speed?

 

[danb35]

The more you write to a USB stick, the faster it dies. Database applications tend to do lots of writes. You do the math.

USB sticks work well for most people, most of the time, for FreeNAS. They're nearly universally available and cheap. They're also easily available in capacities that make sense for the FreeNAS boot device. When they do fail, as long as you've backed up your config file, it's pretty much a non-event--install to a new one, upload the config file, reboot, and you're up and running again. SSDs are pretty widely available, but cost more, and tend to be of larger capacity than is of any real benefit for a FreeNAS boot device. They're faster, but that isn't much of a benefit with FreeNAS, because you aren't booting the server very often, and the software mostly runs from RAM.

Of the three factors you mention, a gigabit Ethernet connection would probably be the bottleneck, but I guess it would depend on the drive. SATA1 is 1.5 Gb/sec (and of course 2 and 3 go up from there), but I guess it's possible that some drive could have less than 1 Gb/sec throughput.

 

[pirateghost]

You should NOT attempt to use the OS drive for any other purpose than the OS. Do NOT install things on the OS, use a jails dataset for jails, on the pool.

USB is recommended for the OS, because most of the OS actually runs in RAM. Your bottleneck will be the network. But a few xbmc clients will not saturate a gigabit link.

Personally i went away from the xbmc/MySQL configuration a couple of years ago and moved to Plex. Best move i could have made for that.