What happens if you concurrently erase, e.g., 4 3390-3 volumes?
I suspect that your calculated "effective" data rate will be higher.
Generally true, depending on the configuration. If the CU has FICON
channels and/or multiple channels, then the disks can be erased
concurrently, subject to bottlenecks within the control unit.
During the development of FDRERASE, we found erasing concurrent disks
that are in the same RAID rank or on the same physical disk (depending
on the vendor and configuration) rapidly reaches a saturation limit, so
we added code to identify the internal disk location and limit the
number of concurrent erases to the same location. By default we limit
to 8 per physical disk/rank, and 64 concurrent total but these can be
overridden by the customer.
But, yes, concurrent erases do achieve higher total data rates.
Also, in my test I used an option which requires a complete track-sized
record to be sent down the channel, but if you are erasing with just
binary zeros, we only send a truncated and the control unit pads with
zeros. This permits more concurrent I/O operations per channel.
We have a lot of stats, but they are very dependant on the vendor,
model, and configuration, so I won't quote them here. My post was just
to show that you can achieve high write rates on a single disk in modern
CUs.
--
Bruce A. Black
Senior Software Developer for FDR
Innovation Data Processing 973-890-7300
personal: [EMAIL PROTECTED]
sales info: [EMAIL PROTECTED]
tech support: [EMAIL PROTECTED]
web: www.innovationdp.fdr.com
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