[Info-vax] VMS to VMS data copy options/performance when losing a DECnet link

[Chris Townley]

On 14/04/2022 15:59, Rich Jordan wrote:
> On Friday, April 8, 2022 at 10:56:00 AM UTC-5, Steven Schweda wrote:
>>> [...] backup to local disk savesets (using the /DATA_FORMAT=COMPRESS
>>> option) [...]
>>
>>> [...] fix the attributes, and restore them because doing even a zero
>>> compression encapsulating ZIP takes too much time for the larger
>>> savesets (ZIP would preserve the backup saveset file attributes).
>> If all you wanted Zip+UnZip to do was preserve the attributes of a
>> BACKUP save set, then I wouldn't bother. There are enough DCL scripts
>> floating around which can restore them in near-zero time.
>>
>> It might be worth a quick experiment to see whether BACKUP without
>> compression followed by Zip with compression makes any sense.
>>> The current VMS to VMS is done with DECnet copies of individual files,
>>> [...]
>>
>> The principal advantage of new DECnet (ising IP) is that it works
>> like old DECnet.
> 
> 
> did a couple of quick tests.  For 25-50GB backup savesets on the RX2800s, run to local disks with backup parameters optimized (and RMS), composite time for compressed backup and ZIP with no compression was about 15% shorter than backup without compression and ZIP "-V6"   (from 6 to 9 got very little more compression in our test but added a fair amount of ZIP time).  The system disk backup done while booted from an alternate boot disk, which is our smallest disk, the times were almost even.  So for now we're sticking with backup doing the compression.
> 

Have you tried zip -3 (or -2) ? You get a little less compression, but a 
much lower CPU load/elapsed time

-- 
Chris