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Hi all,
I am currently in the process of automating some capacity reporting but I have come across a discrepancy I can't work out why,.
When I run a df -g on a volume I can see the snap reserve is close to 4.5TB
/vol/*********/ | 7700GB | 5061GB | 2638GB | 66% /**********/ |
/vol/***********/.snapshot | 3300GB | 4643GB | 0GB | 141% /vol/*********/.snapshot |
When I run the following command in powershell
get-nasnapshot $vol.Name | foreach-object{$VolumeSnapSize += $_.Total }
$snapsize = [Math]::Round(($VolumeSnapSize/(1024*1024*1024)),0)
It gives me at total of 7604GB.
Is this because of dedupe on the snapshots? I am stumped and it really throws my reporting out!
Appreciate any help
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Sorry, this probably isn't going be much help but I've tried your code against one of our volumes which has dedupe enabled and the output looks to be correct and consistent with ontap. This was against 8.0.3.
/vol/*******/ | 5120GB | 2882GB | 2237GB | 56% /vol/*******/ |
/vol/*******/.snapshot | 0GB | 985GB | 0GB | ---% /vol/*******/.snapshot |
Powershell output: 985
I've tried setting the snapshot reserve to various amounts to see if that was somehow throwing the output, it didn't make any difference, but then I wasn't really expecting it to.
Have you tried breaking down the output a little and checking the output on a per snapshot basis? Something like:
get-nasnapshot $vol.Name |
foreach-object{
$CurrentSnapSize = [Math]::Round(($_.Total /(1024*1024*1024)),0)
Write-Host $_.Name " " $CurrentSnapSize
$VolumeSnapSize += $_.Total
}
Maybe a more verbose output will give you a pointer as to where it is going wrong.
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Hi Paul,
You definitely understand the problem correctly. Summing the snapshot sizes won't take into account clones or dedupe, so you are likely to get a bad result.
Fortunately, you can use the "Cumulative" property to get the same output as the df command:
(Get-NaSnapshot myvolume | measure -Maximum Cumulative).Maximum
Or if you like formatted data sizes:
(Get-NaSnapshot myvolume | measure -Maximum Cumulative).Maximum | ConvertTo-FormattedNumber -Type datasize
That should get you within rounding error of the df command.
Cheers!
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Thanks Eric, unfortunately still getting a completely different number!
ashley cook, I outputted the size of each snapshot which gives me the 7TB:
(0151748487)_prd_std_T3_b28_01_r.26705 13
smvi_Clayton-std-daily-01_novmsnap_20120609222000 219
smvi_Clayton-std-daily-01_novmsnap_20120610222000 223
smvi_Clayton-std-daily-01_novmsnap_20120611222000 476
smvi_Clayton-std-daily-01_novmsnap_20120613222000 256
smvi_Clayton-std-daily-01_novmsnap_20120614222000 296
smvi_Clayton-std-daily-01_novmsnap_20120615222000 491
smvi_Clayton-std-daily-01_novmsnap_20120616222000 394
smvi_Clayton-std-daily-01_novmsnap_20120617222000 249
smvi_Clayton-std-daily-01_novmsnap_20120618222000 275
smvi_Clayton-std-daily-01_novmsnap_20120619222000 234
smvi_Clayton-std-daily-01_novmsnap_20120620222006 337
smvi_Clayton-std-daily-01_novmsnap_20120622222000 403
smvi_Clayton-std-daily-01_novmsnap_20120623222000 224
smvi_Clayton-std-daily-01_novmsnap_20120624222001 226
smvi_Clayton-std-daily-01_novmsnap_20120625222000 343
smvi_Clayton-std-daily-01_novmsnap_20120627222000 258
smvi_Clayton-std-daily-01_novmsnap_20120628222000 256
smvi_Clayton-std-daily-01_novmsnap_20120629222000 365
smvi_Clayton-std-daily-01_novmsnap_20120630222000 265
smvi_Clayton-std-daily-01_novmsnap_20120701222000 136
smvi_Clayton-std-daily-01_novmsnap_20120702222000 143
smvi_Clayton-std-daily-01_novmsnap_20120703222000 137
smvi_Clayton-std-daily-01_novmsnap_20120704222000 139
smvi_Clayton-std-daily-01_novmsnap_20120705222000 151
smvi_Clayton-std-daily-01_novmsnap_20120706222001 242
smvi_Clayton-std-daily-01_novmsnap_20120707222000 153
smvi_Clayton-std-daily-01_novmsnap_20120708222000 139
smvi_Clayton-std-daily-01_novmsnap_recent 84
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Erick using this line: (Get-NaSnapshot myvolume | measure -Maximum Cumulative).Maximum I get the below:
prd_std_T3_b28_01: 7654244847616
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Very odd, I can't think of a reason for this.
What I was going to suggest was check the verbose output against System Manager, so you get a view of each snapshot and the cumulative total. I was hoping that might give you an indication of where the output was differing from ontap.
I don't think dedupe should be skewing the output. Certainly when I ran that code the figures returned reflected the dedupe savings. What version of ontap are you running? Just thinking something in the API may have changed between versions.
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Hi Ashley, 7.3.6.
It's very weird as System Manager is reporting the 7TB as well...
|
Kind of throws out my capacity reporting completely...
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I'm stumped sorry. Maybe someone else running 7.3.x could take a look at their system to see if the results are consistent with what you are seeing?
I've seen disparity between what ontap and operations manager report previously, this has been where seemingly different calculations were used for the dedupe savings. Nothing quite like this though.
Sorry I can't be of more help.
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Yep it's got me completely stumped as well... Need to start again with my reporting and have a think how I can get around it.
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Just to throw another curve ball get-nasnapshotreclaimable (unfortunately this method is too slow if I was to use it across all filers) displays a different snapshot size (more consistent with df -g) than what is displayed in the get-nasnapshot and system manager!!
Very weird!