Need to switch from RAID 1 to 5 or 1+0

[russrimm]

I have a DS918+ with 4x4tb drives. <3gb total is in use.
I'm using it for general storage and to host Hyper-V VMs (.vhdx) via iSCSI to my lab. I ended up picking RAID 1 for all 4 drives. Now i'm thinking I want better performance so thinking about RAID 5 or 1+0.
Since I have less data than a single 4tb holds, 1) what's the best RAID for me if I'm not too concerned about running out of space but I want my VMs to be fast (I already put 16gb ram and 2x256gb ssd cache modules in it) and 2) how do I get there from here? Could I somehow get it back to JBOD without blowing it away, moving it off and back on, etc? I do actually have a DS213j with a 3tb drive I could move it to I suppose now that I think of it.
What's my best option?

 

[Rusty]

I have a DS918+ with 4x4tb drives. <3gb total is in use.
I'm using it for general storage and to host Hyper-V VMs (.vhdx) via iSCSI to my lab. I ended up picking RAID 1 for all 4 drives. Now i'm thinking I want better performance so thinking about RAID 5 or 1+0.
Since I have less data than a single 4tb holds, 1) what's the best RAID for me if I'm not too concerned about running out of space but I want my VMs to be fast (I already put 16gb ram and 2x256gb ssd cache modules in it) and 2) how do I get there from here? Could I somehow get it back to JBOD without blowing it away, moving it off and back on, etc? I do actually have a DS213j with a 3tb drive I could move it to I suppose now that I think of it.
What's my best option?

Regarding raid conversions. You will need to backup, destroy the volume and create a new one. In place conversion in your case is not possible.

Regarding type. You are aware of storage possibilities with 5 or 1+0 so won’t mention it here but my suggestion is to stick with Raid5 instead of 10. There were some intesive tests on the old forum and it turned out that 5 is in fact faster then 10. Also if you lose 2 drives in r10 in the same pair you lose it all, as I’m sure you are aware. If space is not a priority then maybe r6 would be better then r10 (more piece of mind).

Personally I run r5 in my 918 with one cold spare. But I needed to maximize storage vs speed/redundancy.

Bottom line is you will have to nuke the volume no matter what you choose.

 

[Gerard]

If space is not a priority then maybe r6 would be better then r10

What’s better between r5 and r6?

Personally I run r5 in my 918 with one cold spare.

So you have 3 of the 4 disks within the 918 running r5, and the 4th disk is setup as a cold spare. Why not do hot spare?

 

[Rusty]

What’s better between r5 and r6?

Speed vise not much if any at all in a 4 drive combo. The main thing is one more drive for redundancy.

So you have 3 of the 4 disk within the 918 running r5? And the 4 disk is setup as a cold spare?

No, I have 4/5 in R5 (so 3 drive total capacity and 1 drive redundancy) and a 5th one outside the NAS as "cold" spare that's ready to be inserted as a replacement.

 

[jeyare]

@ russrimm:
First, there is no generic answer which RAID is better & as Rusty wrote RAID is not a Backup. The biggest difference between RAID 1,5,10 is how it rebuilds the disks. RAID 1 & 10 only reads the surviving mirror and stores the copy to the new drive you replaced. Your usual read and write operations are virtually unchanged from normal operations. However, if a drive fails with RAID 5, it needs to read everything on all the remaining drives to rebuild the new, replaced disk. Compared to RAID 10 operations, which reads only the surviving mirror, this extreme load means you have a much higher chance of a second disk failure and data loss.

So, as you wrote, you have DS918+.

Second: do you need your VMs available when you leave the NAS operation site? If yes, you have to count with a Hot spare disc/s. Then you have to take into your consideration (a primary target):
a) fast data availability (Read/Write performance) from your LUNs with a possible small time loss during automatic RAID rebuild. There is just one and only option for RAID 1 and your DS918+ together with 2 Hot spare discs.
b) medium/low data availability (Read/Write performance) from your LUNs with a possible long time loss during automatic RAID rebuild. There is just option for RAID 5 and your DS918+ together with 1 Hot spare discs. Both of them RAID 1 & 5 have Single-drive failure fault tolerance.
Then Version a) is better, because you have 2 Hot spare discs.

For the RAID 10 your machine is too small (just 4 bays).

But if you don't care about a automatic RAID rebuild or VMs availability during your unavailability (vacation, ...), there are other options for you (except RAID 5 + Hot spare):
c) single RAID 1 or two RAID 1 with no Hot Spare discs
e) RAID 6 with Low Read/Write performance with no Hot Spare discs
f) RAID 10 with no Hot Spare discs

Remember to always use identical disks when creating a RAID 1 & 10 array. The disk geometry (number of heads, cylinders, etc.) is critical and it is strongly recommended NOT to use dissimilar disks.