Backup & TF-867 Performance Issues

Backup & TF-867 Performance Issues

Post by Bob Lombar » Tue, 24 Mar 1998 04:00:00



All:
basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
on SDI and HSC.

We are experiencing what I consider to be *really* slow backup, about
22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

Would going to a larger blocksize on the tape improve things ? (no
unusual block sizes on disks)  How about moving the tapes to a DSSI
controller by themselves ?

As an aside, is there a DSSI interface for the HSC-60 ?

TIA
Bob

 
 
 

Backup & TF-867 Performance Issues

Post by Scott Viet » Tue, 24 Mar 1998 04:00:00



> All:
> basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
> 60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
> on SDI and HSC.

> We are experiencing what I consider to be *really* slow backup, about
> 22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

> Would going to a larger blocksize on the tape improve things ? (no
> unusual block sizes on disks)  How about moving the tapes to a DSSI
> controller by themselves ?

1. Yes /BLOCK=65535 always helps with DLT.

2.  Why not upgrade your tapedrive to something newer?  Use
a DSSI-to-SCSI converter (HSD10) and go with a TZ877 or TZ887
and some CompacTape IV tapes.  You'll love it!

Quote:> As an aside, is there a DSSI interface for the HSC-60 ?

Don't believe there is.  HSC is only CI on the input, STI andSDI on the
output side (did the k.SCSI cards work in the
HSC60?).

-Scott Vieth

 
 
 

Backup & TF-867 Performance Issues

Post by Richard Tomki » Tue, 24 Mar 1998 04:00:00


I'll bet your system is also suffering some performance problems. Take
those backups and write them back onto the disk. Your disks are
fragmented, and indexf.sys is probably all over the disk too with an
excessive amount of extents. Analyse your disk usage carefully and then
intialize your disk providing a larger pre-allocated space for indexf.sys
and then when you restore, do so with /noinitalize.
rtt

--
Views expressed are the author's alone, and not necessarily those of Digital Equipment Corporation. As required by new Digital Internet Policy #1.

This mind left BLANK intentionally!

 
 
 

Backup & TF-867 Performance Issues

Post by Andy Goldstei » Fri, 27 Mar 1998 04:00:00



> basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
> 60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
> on SDI and HSC.

> We are experiencing what I consider to be *really* slow backup, about
> 22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

Yeah, that's pretty slow. Aside from getting a faster tape drive, you
should also consider the state of the file structure on the disks. Are
these big database files, or lots of small files from interactive users
or whatever? If you have a lot of the latter, make sure BACKUP is
running with sufficient quotas to allow its optimized file reading logic
to work. See the section in the System Manager's Guide titled "Setting
Process Quotas for Efficient Backups" (10.7 in the V7.1 doc set). This
stuff matters for all backups, but is particularly important for lots of
small files.
 
 
 

Backup & TF-867 Performance Issues

Post by Hoff Hoffm » Fri, 27 Mar 1998 04:00:00



:>
:> basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
:> 60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
:> on SDI and HSC.
:>
:> We are experiencing what I consider to be *really* slow backup, about
:> 22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.
:
:Yeah, that's pretty slow. Aside from getting a faster tape drive, you
:should also consider the state of the file structure on the disks. Are
:these big database files, or lots of small files from interactive users
:or whatever? If you have a lot of the latter, make sure BACKUP is
:running with sufficient quotas to allow its optimized file reading logic
:to work. See the section in the System Manager's Guide titled "Setting
:Process Quotas for Efficient Backups" (10.7 in the V7.1 doc set). This
:stuff matters for all backups, but is particularly important for lots of
:small files.

  Also consider performing an image BACKUP and restoration of the volumes,
  as this will resolve any disk fragmentation issues that might be around.
  (I run one of these defragmentation passes from every six months or so,
  to every couple of years, depending on how full the volumes get and how
  reasonably the RMS extention settings are configured on the various
  applications.)

  As a quick test, find a big, recently-created file -- of (say) 5000+
  blocks, and use DUMP/HEADER to see how many "map area words" are in
  use.  In general, the larger this number, the more fragmented the file.
  Files extended over long intervals -- such as the system operator log
  file -- tend to be more fragmented (normally), while executable images
  and any files that are created relatively quickly should have relatively
  fewer fragments.

        --

  And check for sufficient paged and non-paged pool -- if you cannot
  remember when the last pass of AUTOGEN with FEEDBACK was run on this
  system, it's probably time to run it again.  :-)

 -------------------------- pure personal opinion ---------------------------

  note to those folks not contributing spam -- there is no ZZ in my address

 
 
 

Backup & TF-867 Performance Issues

Post by Daniel Esbense » Wed, 01 Apr 1998 04:00:00



>All:
>basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
>60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
>on SDI and HSC.

>We are experiencing what I consider to be *really* slow backup, about
>22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

>Would going to a larger blocksize on the tape improve things ? (no
>unusual block sizes on disks)  How about moving the tapes to a DSSI
>controller by themselves ?

>As an aside, is there a DSSI interface for the HSC-60 ?

Hello,

What are your BACKUP qualifiers?

And, BACKUP a small file and then do a:

  $ backup/list tape device:xxx.bck/save
   (or whatever your tape device and backup set were called).
Then, look at how many BUFFERS were allocated.  If less than 500 or so, your
backups can be greatly sped up.

Of course, our company also sells a product called:

  Dynamic Tape Accelerator -- speeds up all write-to-tape operations.

See  http://www.ttinet.com/

Dan E.
Director of Advanced Research
Touch Technologies, Inc.

 
 
 

Backup & TF-867 Performance Issues

Post by d_bra.. » Wed, 01 Apr 1998 04:00:00



>>We are experiencing what I consider to be *really* slow backup, about
>>22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

>>Would going to a larger blocksize on the tape improve things ? (no
>>unusual block sizes on disks)  How about moving the tapes to a DSSI
>>controller by themselves ?

Couple of important qualifiers involved here.  First is to be sure to use
"/cache=tape" to use the little bit of cache your DLT drive has.  The DLT
is a pig when it comes to repositioning.  If your data stream is interrupted
the tape will stop.  It takes about a second to reposition.  If you listen
to your tape drive during backups you should be able to tell if it is
streaming properly or not.  The worst case scenario is that in a given
minute of your backup operation the tape is recording data for 30 secs
and repositioning itself for the other 30 secs.  That is a pretty poor
duty cycle.

Other param is "/block=65534" or whatever the max is for your version of
vms that you are running.

I would guess the Dynamic Tape Accelerator product uses a caching scheme
to keep the DLT streaming properly and a few other bells/whistles to get
the DLT to make its biggest performance numbers.

I move 2.9 Meg/second on a TZ88* off of an HSJ30.

Good luck,  Doug

 
 
 

Backup & TF-867 Performance Issues

Post by Nigel Bark » Fri, 03 Apr 1998 04:00:00



>:>
>:> basic info: VAX 6620 with 1 DSSI controller, 1 SDI controller and an HSC
>:> 60 hung off the CI bus.  TF-867 and 12 RF35s of DSSI controller , RA92's
>:> on SDI and HSC.
>:>
>:> We are experiencing what I consider to be *really* slow backup, about
>:> 22hrs to backup the 12 RF35's (10gb) & 6 RA92's with a verify.

Agree with all the other comments but the quickest fix that would
reduce your backup time by half would be to omit the verify pass.
Modern tape drives are pretty damn good at error correction. It was
different in the days of open-reel magtapes when V1 of VMS backup was
written and that is why it's still there.
--

Now on the sunny Cote d'Azur
 
 
 

Backup & TF-867 Performance Issues

Post by Liffe Administration and Managemen » Fri, 03 Apr 1998 04:00:00




<SNIP>

> Agree with all the other comments but the quickest fix that would
> reduce your backup time by half would be to omit the verify pass.
> Modern tape drives are pretty damn good at error correction. It was
> different in the days of open-reel magtapes when V1 of VMS backup was
> written and that is why it's still there.
> --

> Now on the sunny Cote d'Azur

And if my memory serves me correctly, when BACKUP got rewritten/optimised
at V5.2 the
verification mechanism was left well alone. Thus, the verify pass can take
many times longer
than the backup in some circumstances.
 
 
 

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