2021-08-27 12:50:14 UTC
I would like to expose you an issue with the hope that you can help me to solve it in the best way.
We have OpenVMS 8.4 clusters connected to a full SSD 3PAR storage box via a FC SAN.
We have thin provisioning activated on the 3PAR meaning that we make some “overbooking” with the disk size. We can’t have all disks presented with 100% used space because we don’t have that physical disk space available.
The 3PAR use the free space available on each disk as a common free space pool available to ensure the used size increase of all the disks. (Don’t ask me more, I’m OpenVMS system manager, not Storage manager)
On OpenVMS, a simple DELETE doesn’t tell to the 3PAR that this deleted area is available to be part of the common pool. The 3PAR still considers that location as used.
With DELETE/ERASE, “the storage location is overwritten with a system specified pattern so that the data no longer exists.”
So, I had to implement something that will make an erase operation.
I though to put in place a SET VOLUME /ERASE_ON_DELETE but I’m afraid that severe performance decreases will occur, especially on heavy used disks (creating and deleting a lot of files).
So I made the choice of DELETE/ERASE.
Twice a week, I create 10 MB dummy files until the disk if 95% Full. Then I initiate a DELETE/ERASE of those files. The delete is made one by one to verify that something else is not busy to fill in the disk. If it is the case, I make a simple DELETE for the rest of the files which is more performant.
I don’t create a big file because the DELETE/ERASE could take many time and the size is not available during the operation. This could compromise the used space increase requested by the application.
My problem is that for big disks (800GB) with a low used space, we create thousands and thousands of files and the DELETE/ERASE takes days.
Do you see another way of working ?
I checked the defragmenter, there is a /CONSOLIDATE_FREESPACE but not a “/ERASE_FREESPACE” option
I was hoping to find something in OpenVMS that could act in background, all the time without impacting the performances.
Thanks for your help.