How much space per gig of ram?

[RichTJ99]

Hi,

I am about ready to buy my 6x WD Red drives (system specs in sig)

I am debating on getting either 4TB drives or 6TB drives (6x). My test system has a number of virtualbox machines running, a plex server, & hopes of minidlna in the future.

I could see that while the system has 32gb of ram, I might use 8 or so for various windows boxes & jails, etc. If thats the case am I better off with the 4tb drives or 6tb drives.

The price difference between the group purchase is $600 dollars. Any thoughts on what makes the most sense?

Thanks,
Rich

 

[SweetAndLow]

Workflow required and minimum performance expectations?

You should be fine with 32GB, the real issues is when people try to use 4-8GB with big pools.

 

[jgreco]

As the person who originally bumped the minimum RAM requirement up from 6 to 8GB, and who authored a rather deliberately nebulous section about RAM sizing vs pool sizing in the user manual, let me assure you that as long as you're not stupid-small or way-out-of-range, you'll be fine. At 32GB, you can easily run a 36TB raw pool. You could run a 48TB pool. But as you get larger, it'll get slower. In sometimes nonobvious ways.

One thing you should actually consider is that if you get the larger disks and don't try to use all the space, it'll be faster. Read any of my posts on ZFS and fragmentation. Some include a pretty graphic that shows you're best off keeping the pool below 50% utilization. So guess what? The smart thing to do? Get the bigger drives and don't use the extra space. It will come back to you as speed.

 

[RichTJ99]

So if i use 8gb of ram for VM's leaving 24 GB for the system and get the 6x 6tb drives that would be OK?

 

[jgreco]

Yes, it'll be fine.

 

[RichTJ99]

What about 10x 2TB drives vs 6x 6TB drives? Mainly because I have the 2TB drives & am not sure what else to do with them.

 

[jgreco]

What sort of pool design were you thinking of? Also, be aware that you can have more than one pool if that is helpful.

As long as we're talking pool design, if you have a bunch of 2TB drives, those could be really attractive for a dedicated pool to run your VM's off of. With the X10SL7 you have lots of connectivity so you could put the 2TB's on as mirrors, get a fairly fast VM datastore, and then still acquire some 4's or 6's for other data storage.

 

[RichTJ99]

So I bought the 6x 6TB WD Reds & they are in transit. The current setup (6x 2TB drives) seems to have slowdowns with the VM's. If I boot to many VM's at the same time (i have been testing/playing) or do something data intensive (such as connect to a 20GB MS Exchange account with outlook), the all the VM's seem to slowdown.

What is your suggestion with the 2TB drives for VM usage? Not using them as RaidZ2 drives but as single mirrors?

 

[jgreco]

Yes, the problem with RAIDZ is that the way random I/O works, it is very poorly optimized for small reads and writes, such as what happens when a disk file is pretending to be a virtual hard drive.

https://forums.freenas.org/index.ph...reenas-as-vm-storage.40086/page-3#post-254320

 

[RichTJ99]

Interesting reading on the VM's - thanks!

So to confirm, I should use the 6x 6TB drives for data storage (non VM related), backups, media files for streaming - basically everything except VM's.

Then you are saying I can take the 2TB drives & set them up for the VM storage. Should it be setup as a regular mirror (not RaidZ anything)? My VM's dont do much at this point but as I said they seem to keep mysteriously crashing.

My plan now is to leave the Windows 7 PS3 Media server VM running to see how it all goes. I have a Windows 8 VM running mainly to check email.

I would love to get the Windows 2012 server virtualized & running on the freenas box - assuming I can use the 6TB drives to store windows backup files. It should be very interesting!

 

[jgreco]

Place anything IOPS-stressy on mirrors. The 2TB disks are probably ideal for that. This might include backups if your backup software does anything fancy like data deduplication, but does NOT include backup software that merely stores images (compressed or otherwise) of a disk, or ZIP files, or anything like that. Place any runs of long sequential bytes (ISO files, ZIP files, media files, etc) on a RAIDZn of the 6TB disks. Also try to keep utilization on the mirror pool at a low percentage (less than 50%) for better chances of optimal behaviour.

 

[RichTJ99]

So i have two camera DVR's that are constantly recording data & saving them to local servers. One of the two I can probably use as a VM. Ideally i would like all camera server data to be dumped on the 6x 6TB drive. It would be a constant stream of saving data that gets overwritten. It would be constant network activity and constant disk activity (at least based on the current two boxes).

Can I use the larger raidz2 volume for it?

 

[RichTJ99]

So - would this be the preferred Volume to use for better virtualbox performance? Better IOPS?

I feel like i keep confusing mirrored stripe, or stripped mirror.

Is there any data protection for this setup - if I lose a drive or something?

 

[jgreco]

"Striped mirror" and "Mirrored stripe" are both equally not-real-good ZFS terminology.

What you want are multiple vdevs, where the vdevs are (probably two-way) mirrors. That's the layout you show in the image above, and that's going to be good for IOPS.

 

[RichTJ99]

So to confirm, i have 3 Vdevs above:

Vdev1: da0 + da3 (mirror)
Vdev2: da1 + da6 (mirror)
Vdev3: da2 + da7 (mirror)

Shouldnt I have 6TB of storage?

 

[depasseg]

My guess is that configuration pictured is 2 vdevs (each with a 3 way mirror).

 

[Mlovelace]

That picture shows three-way mirror and the projected size confirms as much (3.63TiB). You can create the zpool by adding a mirror then click "add extra device" add mirror, then click "add extra device" add mirror; Then click add volume. Check the zpool layout with zpool status command to make sure its what you want.

 

[RichTJ99]

Is there a way to test IOPS speed? I wouldnt mind playing around with it before committing data.

So this is a single Vdev which is mirrored (and striped also?)

 

[rsquared]

No, it is a single zpool, which consists of three mirrored vdevs. Each row is a single vdev consisting of two mirrored drives.

 

[depasseg]

So this is a single Vdev which is mirrored (and striped also?)

You should really go back and reread the vdev/pool/dataset guide. Each pair of mirrors is a vdev, for a total of 3 vdevs in your pool.

I don't know of an easy way to test for IOPS, and it's much simpler to google search for benchmarks. The issue is identifying what your workload consists of. The biggest unknown to me, is your "number of virtualbox vm's" Only you know what those are, and if they are bursty or sequential, light or heavy.