topic Re: backup qualifiers in Operating System - OpenVMS

backup qualifiers

Marc Van den Broeck — Thu, 23 Jun 2005 03:37:53 GMT

To copy a large file (4 Gb) from disc to disc, backup seems to be faster then copy. Are there qualifiers to speed up the copy or the backup process?

Thx
Marc

Re: backup qualifiers

Jeroen Hartgers_3 — Thu, 23 Jun 2005 03:52:50 GMT

$ backup

example

$ backup/log test.db -
dka100:[000000.dir1.dir2.dir3]*.*

the log qualifier will genarte the message:
%BACKUP-S-CREATED, created dka100:[000000.dir1.dir2.dir3]test.db

Re: backup qualifiers

Marc Van den Broeck — Thu, 23 Jun 2005 03:59:14 GMT

Jeroen,

I guess using the log qualifier will not speed up the process?

Rgds
Marc

Re: backup qualifiers

Karl Rohwedder — Thu, 23 Jun 2005 04:06:44 GMT

You could try different values of
SET RMS /BLOCK=? /BUFFER=?, but one limiting factor will be the fragmentation of the source disk.
For Backup see the various streams about backup performance.

regards Kalle

Re: backup qualifiers

Jeroen Hartgers_3 — Thu, 23 Jun 2005 04:11:49 GMT

the log qualifier will speed down but in this case with 1 file nor realy. if there is a lot of log output by examble een backup restore of a disk it will speeddown the back restore for a match time.

Re: backup qualifiers

Jeroen Hartgers_3 — Thu, 23 Jun 2005 04:14:22 GMT

that's right

Re: backup qualifiers

Jan van den Ende — Thu, 23 Jun 2005 04:18:45 GMT

Marc,

You are DEFINITELY right! /LOG wil slow it down. For each file processed, an output line has to be constructed, and an extra IO must be executed to write that line to SYS$OUTPUT or the specified logfile.
But in this case, an operation on just one file, the effect is very minimal.

@Jeroen:

...
dka100:[000000.dir1.dir2.dir3]*.*

You are playing with matches in a gunpowder storage!
Specifying [000000... in a backup output string generates a toplevel 000000.DIR.
So far, no noticable problem yet, maybe for a long time
BUT, if you process this directory the same way again, you will have created 000000.000000.DIR
And NOW you are in for some fun!

Please, train yourself to NOT use the [000000.xyz syntax in output specifications!

fwiw,

Proost.

Have one on me.

jpe

Proost.

Re: backup qualifiers

Ian Miller. — Thu, 23 Jun 2005 04:21:34 GMT

In VMS V8.2 and V7.3-2 patch kits the default block size for copy was increased to 127 blocks and this has helped copy performance.
The optimim value if using EVA is 124.
If you are not at these versions then use the SET RMS command to increase the default multiblock and multibuffer counts.
Try MBC=124 and buffer count=3 for a start.

Re: backup qualifiers

Marc Van den Broeck — Thu, 23 Jun 2005 04:35:59 GMT

Jan,

my /log remark was ment a little bit sarcastic because the answer of Jeroen was not really answering my question (Jeroen, dont feel offended).
So, dont think nor talk about /log but about qualifiers speeding up the process ;).

Rgds Marc

Re: backup qualifiers

Galen Tackett — Thu, 23 Jun 2005 05:31:31 GMT

/LOG will REALLY slow it down if you're using an old ASR33 or similar.
:-)

Re: backup qualifiers

Ian Miller. — Thu, 23 Jun 2005 05:36:39 GMT

Galen, DMC32 and now ASR33 - you are showing your age :-)

Re: backup qualifiers

Marc Van den Broeck — Thu, 23 Jun 2005 06:29:21 GMT

Karl and Ian,

set rms/block=124/buf=3 did not make any (measurable) difference.

(btw: vms version: V7.2-1)

Rgds
Marc

Re: backup qualifiers

Jan van den Ende — Thu, 23 Jun 2005 06:36:03 GMT

Marc,

in effect the speed transfers of large amounts of data are nearly completely dependant on IO throughput.
So, your hardware config is the main factor.
Then, there are some settings that can (de-)optimise the use of the hardware capability.
That optimisation is mainly done with bufferings, and for that, see previous answers.

About being offended: do you really think that someone so easily offendable can do our kind of work for longer than a few months?

For those that sensitive, we have a saying: "If you can not stand the heat, you have to stay out of the kitchen"

fwiw,

Proost.

Have one on me.

jpe

Re: backup qualifiers

Karl Rohwedder — Thu, 23 Jun 2005 06:36:06 GMT

Btw, what performance do you achieve (on what hardware)?

regards Kalle

Re: backup qualifiers

Marc Van den Broeck — Thu, 23 Jun 2005 06:46:04 GMT

Karl,

with backup it takes 59' to copy 16Gb of files (15 files between 0.1Gb and 2Gb)
from hsz50 disks to an internal 10000 rpm disc on a COMPAQ AlphaServer DS20E 833 MHz.

(btw: backing it up to a dlt8000 is almost 2 times faster)

Rgds
Marc

Re: backup qualifiers

Willem Grooters — Thu, 23 Jun 2005 07:39:08 GMT

Is your target disk shadowed? If so, it _may_ cause slow down.
/BLOCK= may speed up but could prove contra-productive. I have no measurements - just the feeling.
My memory may have faded and blurred, but as far as I remember, COPY will process a file record by record, and BACKUP will copy block(s)-by-block(s). Also, COPY will use the cache, and BACKUP may bypass it. This would explain yhe difference.

Re: backup qualifiers

Jan van den Ende — Thu, 23 Jun 2005 09:01:18 GMT

BACKUP may bypass cache --
make that BACKUP DOES bypass cache.

I just will have to scan trough my Bootcamp notes to find a direct reference, but it has been pointed out in an XFC discussion.

Proost.

have one on me.

jpe

Re: backup qualifiers

Volker Halle — Thu, 23 Jun 2005 09:10:44 GMT

Marc,

with your backup disk-to-disk, you reach about 4.5 MB/sec. If it's twice that fast disk-to-tape, then the output disk probably seems to be the bottleneck.

You could try to disable high-water-marking on the destination disk (SET VOL/NOHIGH), it reduced the duration of my little test by about 10%.

Volker.

Re: backup qualifiers

Jan van den Ende — Thu, 23 Jun 2005 13:07:59 GMT

Marc,

just to make sure, regarding Volkers answer:

ARE the input and output disk 2 separate physical devices?
If so, are they on the same or different controllers? Of what type?

Proost.

Have one on me.

jpe

Re: backup qualifiers

Marc Van den Broeck — Fri, 24 Jun 2005 00:13:07 GMT

Volker,

disabling high-water-marking on a disc is one of the first things I do on a disc I have to use.

Jan,

from hsz50 disks to an internal 10000 rpm disc on a COMPAQ AlphaServer DS20E 833 MHz.

Rgds
Marc