On Wed, 13 Mar 1996 14:02:24 -0500 Larry Anta said:
>My questions are:
>1) Why is the "TOTAL NUMBER OF BYTES TRANSFERRED" so low?
If you are using compression, this will lower the number. The number
reported is the amount of compressed data that was transferred. I assume
this was an initial backup. If not, another reason the number could be low
is that you are not backing up files which have not changed. Another
reason is that perhaps you have excluded some files using the exclude
facility.
>2) Can any of these numbers be trusted? I calculate a data transfer rate
> of 433.22 KB/sec (1.9GB/4,598.83sec).
I believe that the "transfer rate" reported by ADSM is the transfer rate
for when data was actively being transmitted. Wait times are not included.
So if your client is spending time compressing data, and not transmitting
it, that time does not get calculated into the transfer rate. For this
reason, the reported transfer rate should always be higher than simply
dividing bytes transferred by wall clock time.
>3) And finally, if we really are getting only about 0.5 MB/sec
> throughput, why is it so slow? 3590-B11s are rated much much higher.
> I wasn't expecting the theoretical maximum, but 0.5 MB/sec is not even
> close.
First question is are you backing up directly to 3590 tape, or are you
going to disk first? Second question is what type of disk are you using
for your database, and how much is it spread out across disks/channels?
I believe that database update activity is often a limiting factor, and
can prevent you from seeing anywhere near rated tape performance. The
smaller the files you are backing up, the more this becomes an issue.
I have not figured out how to optimize database update activity yet, but
this is become a more and more important issue for us.
>
>Thanks in advance.
>
>/ Larry Anta | Ryerson Polytechnic University \
>\ lanta AT acs.ryerson DOT ca | Toronto, Canada (416) 979-5000 Ext.6817 /
..Paul
Paul Zarnowski Phone: 607/255-4757
Cornell Information Technologies Fax: 607/255-6523
Cornell University US Mail: 315 CCC, Ithaca, NY 14853-2601
|
