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ADIC Scaler 24 - is compression working
I'm using Networker 7.3.2. I am doing a backup to disk and then cloning to tape. The tape I'm writing to is a SDLT600 inside an ADIC Scalar 24. The write speed is 30 MB/s. It's putting about 375G on each tape. The mt command shows compression is enabled. But...
The Scaler 24's front panel has an icon that is visible when hardware compression is turned on. During the clone operation this icon is NOT on. According to ADIC support site, this icon should be visible if hardware compression is working. If not, it may be a backup software problem...
Does anyone have any thoughts on whether compression is or is not working here or has anyone seen this with a Scalar 24?
The Scaler 24's front panel has an icon that is visible when hardware compression is turned on. During the clone operation this icon is NOT on. According to ADIC support site, this icon should be visible if hardware compression is working. If not, it may be a backup software problem...
Does anyone have any thoughts on whether compression is or is not working here or has anyone seen this with a Scalar 24?
ble1
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September 19th, 2006 14:00
visible when hardware compression is turned on.
During the clone operation this icon is NOT on.
According to ADIC support site, this icon should be
visible if hardware compression is working. If not,
it may be a backup software problem...
I would be interested to hear how can setting set on hardware (library) be a problem of backup software application as those two don't care about each other?
is or is not working here or has anyone seen this
with a Scalar 24?
SDLT600 should have 300/600 1:2 compression ratio (and 36/72 speed). What you said seems to indicate minimum if none compression according to speed and capacity used.
First thought was that perhaps you use software compression so there is nothing for drive to compress thus no compression icon, but even then I would expect more data on volume. That is if you get persistent capacity value of 375GB.
To explain how it works when you get hardware compression:
- stream is sent against logical OS device (eg. nsrmmd sends data to /dev/rmt/0cbn)
- above is handle by native device drives (eg. st)
- data is read by drive and compressed
In short, if you use tar/cpio/dd you should see the same.
You easily check from display panel of the library if compression is enabled or not on devices.
Of course, there is something else that I just thought of - what is the device you use? Under some operating system for compression to be used you must use device instance set for compression (eg. AIX, Solaris). That could be another thing that may play the role here.