EqualLogic ps6100 reserve snapshot and volumes quota

Hello,  

 If you are not using snapshots you can absolutely set the snapshot reserve to zero (0).  It's an amazing feature that you are giving up of course, but if you aren't going to use it then go ahead and set all volumes to zero. This will free up space.  It is strongly recommended and is a best practice when resizing volumes to allocate snapshot reserve to that volume and create a snapshot BEFORE you increase or decrease a volume size. Especially if you are shrinking a volume. (Note: You must shrink the filesystem FIRST, the array is not filessystem aware)   Having that snapshot will allow you to instantly recover from a mistake. E.g. you shrank it too far, or extended an MBR volume past 2TB.  

Re: borrowing.  When you use snapshots, or thin provisioning, you can set a volume to "borrow" free space. So if you did not allocate enough snapshot space for example, it will "borrow" some from other volumes.  In your case I would not enable that feature.   That's all the resze graph was saying you have this much "free" space and this much space to borrowing

 Re: Thin provision. Thin provisioning allows you to have more free space (for things like snapshots) by not pre-allocating all volumes.  HOWEVER, it also does allow you to over-provision your pool.  You can create volumes that if you fill them would exceed the actual amount of storage in that pool.  This will result in offline volumes.  To help guard against that, you can set warning thresholds to alert you as you approach this CLIFF.  Since the product is no longer made I would strongly suggest you do not over provision your storage pools.  If you stay within the limits then using thin provisioning can allow you more headroom. You can then set the warning alerts to 100% or 90% if you want to be alerted as you approach volume limits. 

Finally, NEVER allocate all the space in the storage pool!   The array needs free space to work with for performance reasons.  Again this is where thin provisioning can be helpful.  If your OS filesystems support UNMAP you can reduce the amount of in-use space for each volume giving that back to the free pool. 

Before you do any resizing i would let the expansion process complete. Then set snapshot reserves to zero (0), and thin provision all volumes.  If you can manually run UNMAP (e.g for VMFS Datastores) then do so and see what your free space is then.  Then keep at least 5-10% free after allowing for 100% volume space usage, and grow your volume, or create a new volume. Depending on application, more, smaller volumes work better than one MEGA volume.  

Regards,

Don

hi @dwilliam62 

Thank you.

I followed your advise and went for thin provisioning with zero snapshot.

When I come to the point that I reset the ps6110 with the 7x ssd and 17x spinning disk, what should I do for snapshot? what are they for? Is it like a way to restore data like a backup?

Hello, 

 Snapshots are a point-in-time copy of your data.  You can roll back a volume entirely to that date and time almost instantly.  Or more common you mount the snapshot and restore just the files you need.  So for operations like resize they are very important.  If you make a mistake on a 10TB volume, manually restoring would take a long time. A snapshot is near instant. 

 Also many backup programs work with EQL or AKA "hardware snapshots".  If you have the Host Integration Toolkit for Windows for example,  Exchange, SQL and SharePoint work with EQL snapshots directly.  In fact an Exchange mailbox can be rolled back from within the Exchange GUI.  

 The don't replace backups they allow you greatly augment them. You can schedule snapshots during the day for example.  

 Regards, 

Don