[Info-vax] Reclaim disk space for a 3PAR Storage Box

[Stephen Hoffman]

On 2021-08-30 12:19:51 +0000, Simon Clubley said:

> Hard to believe that this is still a problem on VMS in 2021.

That would be a system that hasn't seen appreciable file system updates 
or a file system replacement in a ~quarter-century, and one that 
remains limited to 2 TiB volumes?

A whole lot has changed with storage and storage I/O since HDDs reigned 
supreme. 12 TB drives, and 4 TB SSDs are now commonplace, among other 
differences.

Without TRIM / UNMAP command support, highwater marking and volume 
erase-on-delete are the usual path for thin-provisioned volumes, and 
also for SSD volumes.

Otherwise, your SSD performance is entirely dependent on on how much 
over-provisioning your SSDs might have and how fast the SSDs can erase, 
when your app gets write-active.

These settings do increase the app and system I/O load, but the 
controllers can retire the commands asynchronously; without having to 
wait for the storage writes to complete.

VSI might want to post some documentation or guidance here, not just 
for thin-provisioned and virtualized storage, but also for anybody 
presently using SSD on OpenVMS. Similar issues lurk...


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