Expanding Storage Pool to 4 SSDs from 2 SSDs on 2012R2?

im.thatoneguy

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Oct 28, 2020
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I have a 2012 R2 server on its last leg and will be replaced soon. But I'm trying to eek it out until PCIe4 is more widely available and stable.

I have a Mirror storage pool with 8x 10k SAS drives and 2x SSDs. I'm seeing solid 500/700MB/s for Write/Read speeds. I would like to fully saturate 10gb. If I added another 2 SSDs to the pool should I see my speeds go up to 1GB/1.4GB (minus overhead)? Or will it just expand the SSD tier to be larger? Or will my sequential read speeds always be off of the HDD tier even if I have 2TB of SSD tier capacity?

Also, is this operation supported without nuking the volume for do I need to transfer everything off to a temp drive before adding an additional 2x SSDs?

Thanks!
 

gregsachs

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Aug 14, 2018
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Is the space set up with Tiering or just a mirror? I think if the space was not setup with a tier, it will be treating all of the drives as the same priority, and just striping the writes across 5 drives. Adding 2 ssds would let you expand, but not change speeds significantly. OTOH, if it was setup as a tiered space, then you can't change the size without nuking is my memory.
 
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gregsachs

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It's currently setup with tiering.
I think with tiering you are stuck, especially on 2012. Only choice would be to blow it away and recreate I believe. I don't think that the SSD tier column size can be changed from 1 to 2 on the fly, to allow striping of the data across drives while still respecting the mirror.
 
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im.thatoneguy

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Virtual Disks though are all that matter not Pools though right? I'm just wrapping my head around storage pools. And pools don't care about columns or specific data arrangements. That's at the disk level. So I have some unprovisioned data on my pool I could add the 2x SSDs. Create a new 2 column Virtual disk on the provisioned space on the drives as a life boat. Then nuke the big disk and return the data.

You do have to specify a pool is tiered. But once it's tiered the particulars are at the virtual disk level?
 

gregsachs

Active Member
Aug 14, 2018
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Virtual Disks though are all that matter not Pools though right? I'm just wrapping my head around storage pools. And pools don't care about columns or specific data arrangements. That's at the disk level. So I have some unprovisioned data on my pool I could add the 2x SSDs. Create a new 2 column Virtual disk on the provisioned space on the drives as a life boat. Then nuke the big disk and return the data.

You do have to specify a pool is tiered. But once it's tiered the particulars are at the virtual disk level?
Possibly? Windows has gotten really funny with things when adding disks to a storage pool, and my memory is that 2012R2 does not have a means of rebalancing the pool free space, which 2016 added. I think if you added 2 new SSD of identical size to existing disk, and expanded the SSD tier, I think the disk is still stuck at a column size of 1 on the ssd tier, and thus unlikely to gain speed. I believe you need to nuke and recreate with columnsize=2 to get a benefit of striping across pairs of SSDs.


I honestly don't remember, and I've done more with 2016 than 2012R2, so it is hard to tell. I ended up moving away from tiered as I got frustrated with it.

This link says you can add SSDs and expand the tier size, but the speed limit should be related to column number, which I believe is locked at creation.
 

cesmith9999

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Mar 26, 2013
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what matters is the column count in the vdisk. and in 2012 R2 to add to a vdisk you had to duplicate all of the disks in the pool on ALL tiers.

You cannot just add 2 SSD's and expect faster throughput. if you add them to the pool. and your vdisk is fixed(not thin). the SSD's will go unused.as the vdisk has all of the sectors allocated on the existing SSD's.

Chris
 
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