I have been experimenting with unRAID, FreeNAS, and a little bit of VMware (but dont have a hardware RAID controller)

Between unRAID and FreeNAS 11 I find unRAID to be much more user friendly and easier to manage, setup and configure VM's.  The state of VM's in FreeNAS 11 is severely lacking.

However there is one thing that is really hurting me with unRAID, the VM I intend to use will have 90GB allocated to its local "C:" drive, and around 2TB or so for its "D:" drive (Windows Server 2016)

For hardware I have:

Xeon 1230v5

32GB DDR4-2133 ECC

2x Samsung 850 EVO's 250GB

4x (old) 1TB WD Red's (2.5")

Dual Gbe LAN, Mellanox 10Gbe

What my experience there is no way to cache writes on the second vdisk (drive D) on the cache drives as it would be way to large.  So when writing to the second vdisk (drive D) a single 1TB drive with 1 parity disk, I hit a whopping 22MB/s, and if I hit all 3x 1TB drives at once i get writes of 7.1MB/s per disk, which is ridiculous.  I know these are not fast drives but writing with RAID 5 instead of XOR seems to be better.

 

Is there someway I can cache writes to the SSD (or RAM) at all? or are there any recommendations for increasing throughput?  I know FreeNAS can cache vdisk (zvol) writes but it is a completely different product (mostly targeted at NAS usage, and I have a perfectly good DS1812+ filled with 3TB drives running, no real reason to replace that)

 

I really want to use unRAID because of the great features it enables me, sure I can use Hyper-V on Server 2016 but unRAID gives me the flexibility to run VM's independently.

 

The only option I can think of is replacing my 1TB's drives with SSD's which isn't exactly inexpensive.

Edited May 9, 20179 yr by SG872

Try with turbo write on.

3 hours ago, johnnie.black said:

Try with turbo write on.

 

^^^^ first.

 

then when you still hate the performance, buy an ssd to put your vm's on. You can get a good samsung 250gb ssd for about a hundred bucks. OR you can spend less on a lesser drive.

Another thing to consider is whether the 1TB drive to be used by the VM needs to be part of the array.   It might be more desirable to have it set up as an Unassigned device outside the array?

So now I have two questions, what is Turbo Write?  and You can have a device outside of the array (or multiple disks) and passes through to the VM?  I assume you cannot use this disk on any other VM's as it is assigned to one specific VM.

 

The local "C" drive will be on a SSD as its capacity will fit, but I want more I/O performance for my "D" drive which would be on mechanical disks than XOR parity can provide.

 

I suppose another option is use the 1TB disks (No parity) and provision say 500GB on each disk as a vdisk for the VM, and have Windows do a software RAID 5?  Not a big fan of that.

 

Edit: I don't intend on having the disks spin down.

 

Hows the write performance in unRAID's version of RAID 1?, say if I got 2x 3TB or 4TB drives

Edited May 9, 20179 yr by SG872

Wondering if anybody has any input in my previous post.  I did look up Turbo Write I will have to re-setup my unRAID system and play with that.

 

Heres another thought though,  What happens in terms of performance of the parity disk a SSD, while the data disks are HDD's?

6 hours ago, SG872 said:

What happens in terms of performance of the parity disk a SSD, while the data disks are HDD's?

Reads and writes would be limited by the speeds of the individual HDD's, with the difference that writing to multiple HDD's simultaneously would happen at full speed of the individual disks until the SSD ran out of bandwidth.

 

However, with the current prices, there is no scenario I can think of that would make sense to have a parity SSD and data HDD. The cost of a sufficiently large SSD would dwarf the cost of the data drives. Either you are made of money and would go ahead with a full SSD array, or you would be using such small data drives you would be losing a huge amount of speed compared to a large modern HDD.

 

Remember, the parity drive must be as large or larger than ANY data drive.