Triple Striped Mirror using Volume Manager

[L3192]

Hello, I'm new to FreeNas and had a question on how to correctly use Volume Manager to accomplish the following:

I have 32-4TB drives and would like to triple mirror and stripe 30 drives and have two spares. When I try using volume manager, it does not seem to like the combinations I'm choosing. So my questions are:

1. What are the best steps to take using Volume Manager to create 10 3-disk mirrors and stripe these to get a Raid 0/1 affect. Note: that I'm looking for the best possible performance with some level of redundancy.

2. From reading this post "https://forums.freenas.org/index.ph...-disks-with-2-striped-and-then-mirrored.7956/"
"When you lose a drive in RAID 0/1 the rebuild affects the entire RAID group, which subjects all the drives to the rebuild. For that reason, I recommend building RAID1 groups and then add them to a pool, which will stripe across the RAID groups to create RAID 10. Avoid RAID 0/1 if possible, especially with SATA drives."

From the above, looks like this may be a better approach, since you will not have the entire raid group affected or am I missing something?

3. I will be doing the same as in question 1 but for 1TB SSD Drives, will the approach change?

Any help or recommendations would be appreciated.

 

[L3192]

Hello, I'm new to FreeNas and had a question on how to correctly use Volume Manager to accomplish the following:

I have 32-4TB drives and would like to triple mirror and stripe 30 drives and have two spares. When I try using volume manager, it does not seem to like the combinations I'm choosing. So my questions are:

1. What are the best steps to take using Volume Manager to create 10 3-disk mirrors and stripe these to get a Raid 0/1 affect. Note: that I'm looking for the best possible performance with some level of redundancy.

[QUOTE=" Please disregard this question, I was able to play around with it and figure it out. I selected "3x10x4tb" and was able to get the triple mirrors"

2. From reading this post "https://forums.freenas.org/index.ph...-disks-with-2-striped-and-then-mirrored.7956/"
"When you lose a drive in RAID 0/1 the rebuild affects the entire RAID group, which subjects all the drives to the rebuild. For that reason, I recommend building RAID1 groups and then add them to a pool, which will stripe across the RAID groups to create RAID 10. Avoid RAID 0/1 if possible, especially with SATA drives."

From the above, looks like this may be a better approach, since you will not have the entire raid group affected or am I missing something?

3. I will be doing the same as in question 1 but for 1TB SSD Drives, will the approach change?

Any help or recommendations would be appreciated.

Would appreciate any help with question 2 through.

 

[Mr_N]

not sure what you mean by "triple mirrors" but if you check 'zpool status' you can see what you've created.

as for the other post yes you should be striping mirrors not mirroring stripes.

 

[gpsguy]

*I* think the OP might be talking about 3-way mirrors. He needs to stop referring to stuff as RAID1/0, 10 and use the proper terminology.


Sent from my phone

 

[L3192]

I figured it out as mentioned above. Nevertheless, comments are welcome!

 

[Mr_N]

So what type of pool did you create with the 3x10x4TB ?

the 10x4tb could be z1/2/3

 

[gpsguy]

You've got your multipliers in the wrong order.

As I suspected the OP was planning "to create 10, 3-disk mirrors and stripe (them)".

So what type of pool did you create with the 3x10x4TB ? the 10x4tb could be z1/2/3

 

[Mr_N]

I'm not the one who put numbers in the wrong order :)

Surely im missing something but how do you make a mirror out of 3 disks ?!?

Are we talking the same thing on 3 drives?

 

[gpsguy]

Here's an example of what a 3-way mirror looks. I pulled it from section 8.1.13 of the documentation (Splitting a Mirrored Pool). With a 3-way mirror, one could lose 2 disks in a given vdev, without losing the entire pool. The volume manager allows one to create a 3-way mirror.

One of our moderators, @jgreco, has a server with 8 sets of 3-way mirrors. He's using it as an iSCSI target with ESXi.

Code:

zpool status
pool: test
state: ONLINE
scan: resilvered 568K in 0h0m with 0 errors on Wed Jul 6 16:10:58 2011
config:

NAME STATE READ WRITE CKSUM
test ONLINE 0 0 0

mirror-0 ONLINE 0 0 0
    da1 ONLINE 0 0 0
    da0 ONLINE 0 0 0
    da4 ONLINE 0 0 0

 

[Mr_N]

sacrificing 20 out of 30 drives seems like alot? what reasons would one have to do that over say 5x6xDrive raidz2 vdevs?

 

[gpsguy]

Start with the last paragraph in this message and work backwards - https://forums.freenas.org/index.php?threads/i-o-performance-planning.40002/#post-250112 The message was written in December, I seem to recall that he's added an 8th vdev since then.

 

[jgreco]

sacrificing 20 out of 30 drives seems like alot? what reasons would one have to do that over say 5x6xDrive raidz2 vdevs?

Probably because mirrors are a hell of a lot faster for block storage than RAIDZ, and 8 three-way mirrors are going to kick the living crap out of five 6 disk RAIDZ2 vdevs.

In a way your question doesn't make any sense, because 6 drive RAIDZ2 vdevs still waste 33% of the space. Why not just stripe them and get the full benefit of all the space?

At a certain point you just have to get over the whole "OMG I'm sacrificing ${X}" thing and just figure out what you need to do in order to get where you need (or want) to be. The ZFS design goal over here is that a single disk failure should not compromise redundancy. This makes RAIDZ2 or three-way mirrors the minimum acceptable standard. I've chosen to use inexpensive 2.5" SATA hard drives rather than SSD or SAS drives, so I feel I can afford more of them. Since I'm doing block storage, RAIDZ2 is poor at that. So the three way mirror thing makes sense.

Is it more expensive than just attaching an external USB disk to a PogoPlug and then storing your data on it? Hell yes it is. But it's also a lot faster. Were I to be doing it over this year, I might well decide instead to go with SSD's, because of the way that prices have dropped in the last year. But even then, things seem like they'd favor three way mirrors.