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 Post subject: Adding disks to a 8440 and set size
PostPosted: Mon Feb 10, 2020 3:08 am 

Joined: Mon Apr 09, 2018 7:19 am
Posts: 13
Hello.

I have an 8440 array with 2 cages (nodes+cage), with 10 1,92TB SSD each. Actually my set size is RAID6 8+2.

I'm adding 4 more disks (same size), 2 on each cage. Should I créate a new CPG with set size 10+2 o it's safe to change actual CPG and launch a tune??

Wich command should I use?? Can it be done in SSMC?? (i'm at versión 3.3.125068)??

Thanks in advance :)

BR


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 Post subject: Re: Adding disks to a 8440 and set size
PostPosted: Mon Feb 10, 2020 6:22 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 1002
Location: Europe
You could change existing CPG to R6 (10+2) but you don't have to.

Personally I would add the drives and do nothing.

Tuning everything to new CPG is time consuming and may be an issue if you're using dedupe. Changing existing CPG will take you from a layout that has optimized RAID 6 to one that doesn't.

If you want to do something, I would replace your old SSMC with the new appliance based version. It has some nice features for all flash systems.

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 Post subject: Re: Adding disks to a 8440 and set size
PostPosted: Mon Feb 10, 2020 6:54 am 

Joined: Mon Apr 09, 2018 7:19 am
Posts: 13
MMmmmm… Yes, I use dedupe+compression in all our volumes.

But how bad is having the "non optimized" raid layout??

Another option is not tune, directly create a new CPG with 10+2 set size and migrate all data to new volumes in this CPG. Maybe more time consuming (of my own time), but less resources consumed and less likely to have problems with dedupe and so...

BR.


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 Post subject: Re: Adding disks to a 8440 and set size
PostPosted: Mon Feb 10, 2020 1:38 pm 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 1002
Location: Europe
If you're going to tune to a new CPG you need free space to support the space used by your DDS. If you're unlucky on an old dedupe version, that would require ~50% free space. If you're using compression you're probably not using old dedupe version but you would still require some free space.

The difference between "good and bad" is on average about 5% on write performance(iops).

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 Post subject: Re: Adding disks to a 8440 and set size
PostPosted: Wed Feb 12, 2020 2:52 am 

Joined: Mon Apr 09, 2018 7:19 am
Posts: 13
MammaGutt wrote:
If you're going to tune to a new CPG you need free space to support the space used by your DDS. If you're unlucky on an old dedupe version, that would require ~50% free space. If you're using compression you're probably not using old dedupe version but you would still require some free space.

The difference between "good and bad" is on average about 5% on write performance(iops).



Yes I have a Good amount of free space, about 50% I guess. The disk adition is in previsión of future projects. we had bought 8 new servers for virtualization and have used the discount to add 4 disks (with high discount :) )

BR.


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