Dell Equallogix PS4100X San question -Storage expanson.

Hello, 

 The RED negative is showing that you are reducing the free space. "borrowing" is different from free space.  That's for snapshots or replication. 

 You also want to keep at least 5% unallocated for best performance. 

 I would check your volumes to see if you have snapshot reserve assigned to them, and if you are not using them or not using all the space allocated you can reduce the reserve to free up more space. 

 Also check to see if volumes are thick or thin provisioned.  Thin provisioning will also help you free up space, but don't OVER provision your pool. If you actually run out of space those volumes will go offline as they try to write new data. 

 Thin provisioning also thin provisions the snapshot reserve as well. 

  Why are you trying to grow this volume such a small amount?   Some customers have mistaken the 100% in-use space on the array with actual in-use space the OS sees.  The OS is the only reference you want to use.  The allocation table the OS maintains is what is accurate.  The array records writes.  Deleting a file doesn't update the array unless the OS also sends an UNMAP command.  No all filesystems do that, and if EQL replication is enabled UNMAP is not supported. 

 I see this kind of small size increases in VMware environments frequently due to the in-use space show on the array.  Customer then slowly increase the volume size to get rid of that alert. 

 Regards, 

Don 

 

I did check snapshots and they are not being used and space is not reserved for them.

Volumes are thick provisioned in the san.

As for increasing in small amounts, we were in the starting phases of a migration with larger storage before the Covid-19 shut down all of my state plus they don't have much free space left on the san so we are working to keep them up and running until the client reopens so we can install the new hardware. 

 

 

Hello, 

  Thanks for the reply.  One thing you can is thin provision all the volumes.  that can be done live without interruption.   The host OS is not aware of the change.   Then allocate a small percentage of snapshot reserve to the volume you want to extend.  This will allow you to back out the change in case there's a problem. 

 

FYI: If you do decide to TP the volumes, change the warning level to something much higher than the default of 60%  This prevent alerts in the GUI and e-mails if you have that enabled.  It's on the same Advanced tab under volume properties.  When you enable TP there are sliders on the bottom graph.  You can slide the warning threshold all the way up to 100%. 

 Regards, 

Don 

 

So basically, I can ignore the borrowed numbers, even though it will go to zero since the client is not using snapshots. 

If the san states i can increase the volume to 1.26tb and the volumes are thick provisioned, would there be any harm in adding in the remaining space or should I play it safe like I was going to and add a little bit of space as needed?

 

 

Hello, 

 When you never want to allocate 100% of the space in a pool. 

 Borrowed space is for snapshots and replication.  They will "borrow" free space if enabled, from the free space pool to maintain a snapshot or replica that exceeds the specified limit.   It's a failsafe. 

 You need to look at free space at the pool, not member level.  The member shows how much as been written, the pool how much has been allocated.  If there you have 250GB you could about 170GB expansion.  Leaving about 89GB free.  Which is bare minimum.  

 Regards, 

Don 

 

You need 5% or at least 200GB free space within the pool. Otherwise the EQL will freak out. Check the documention about or ask Dell support.

You can switch to TP volume and back if you want. Also the GroupManager will show you how full the volume already is. So you see if switching to TP brings any benefit. Check all of your volumes......

When using TP we move the warning slider about TP usage to 100% to get rid of the warnings. Same for volume.

Regards,
Joerg

Hello, 

re: 5%.  OK the SAN isn't going to "freak out"  lol   There are other SANs that will stop operating without free space.  What can happen is a reduction in performance on writes if there is little or no free space.  Worse when you use snapshots or replication.  Which this customer is not. 

 The big issue with TP is you can potentially over provision your pool.  Presenting more space than the storage actually possesses.

 One benefit of TP volumes if your OS supports UNMAP you can reclaim unsued blocks to further increase free space.

 Other possibilities are if you have free space on other volumes and the OS supports shrinking you can reduce those volumes and add that to your critical volume.

 Regards,

Don

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