I am happy to hear about your plans to minimise your database updates. As part
of my file systems contains large amount of small files, which are on average
only 5-10x bigger then associated entries in ADSM database, I surely will
profit from it.
On the other side, I also desperately could need speed improvement in tape
handling. I believe simple and sufficient first-step solution might be making
tape buffers much larger - maybe 2 magnitudes larger. I see you plans to do
this for 3590, please adopt this plans for 4mm tapes, too.
To ilustrate why:
I also back-up some file systems with larger files (N x 10MB each).
The OS used are OS/2 and NT, PC´s are PCI Pentii 120MHz and higher, disks
subsytems are fast-scsi with cached controllers, tape subsystem is 4mm-DAT in
DDS2 Format.
Adsm/2 (V1.x) migration from disk to tape, restore, or any other tape <-> disk
operations performs with snake speed of about :
>> 10 MB in the minute, <<
while any other backup program testetd performs with averge speed of
>> 40-50 MB / minute.(*1) <<
Among programs tested is also HP´s Omniback, which also has to do database
updates while backing-up, but it handles tapes in 200 MB chunks, while ADSM´s
chunks are mickey-mouse tiny. Small tape blocks kill performace especially on
hellical-scan devices like DAT.
While ADSM migrates large files from disk pool to tape pool, the CPU usage is
very low on the ADSM server, as well as disk activity, so only tape handling
seems to limit the speed.
*1 the speed depends on compressability of data to be written to tape, and
is at least 30MB/minute for non-compressable data, and up to 100MB/minute for
highly compressable data.
==> Please extend your plans to increase tape buffers to another devices and
another software plattforms.
Juraj Salak e-mail sal AT keba.co DOT at
KEBA Banking phone (732) 7090 461
Gewerbepark Urfahr fax (732) 730910
4040 Linz, Austria
----------
~ Von: Greg Tevis
~ An: Multiple recipients of list ADSM-L
~ Betreff: 3590 performance with adsm
~ Datum: Mittwoch, 27. November 1996 18:39
~
~ Janet Curtis asked about adsm plans for higher performance
~ exploitation of 3590 drives...we have been working on some
~ improvements in driving 3590s. One of the short term
~ enhancements involves larger buffers for writing to the 3590...
~ I believe this will be available soon (if it's not available
~ already...I can't remember)...we have seen promising
~ results in initial testing of it... We are also looking
~ at other enhancements for next year. We won't be able
~ to drive the 3590s near their 9MB/sec rate until we also
~ minimize the associated adsm database updates ( we will never
~ be able to eliminate them so we won't be able to reach the
~ hardware speeds...but we should be able to get much closer).
~ All of these enhancements are only for 3590 on aix...since we
~ have the most control of the device drivers...
~
~ ...greg tevis
~
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