Re: Moving to flash storage
- From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 18 May 2018 00:08:24 -0400
On 05/17/2018 10:15 AM, Matt Adams wrote:
It looks like we might be migrating the big production databases (2 of
them for a combined 40 Tb or so) to a NetApp 8080 Flash storage
device. These database have thousands of concurrent connections and
turn over between 10 G and 30 G of redo per hour.
I seem to vaguely recall a message or two here on the list over the
last couple of years regarding things to watch out for when migrating
to flash storage.
Well, the characteristics of the flash storage are very different from
the characteristics of the spinning disks. The first important
difference is that the difference between sequential access and random
access is much smaller. Make sure to gather new system statistics. Also,
flash disks are much more expensive than rotational disk. So much so
that advanced compression option suddenly starts making sense. The
"compress for all operations" can really save you some space and money.
Benefits of the index scan are much smaller with flash storage. Also, in
my experience, using larger block size like 16k can make some difference
for some kinds of flash memory. Talk to NetApp and ask them for their
recommendations. Reading bigger blocks in bursts can speed things up.
As for the transfer rates, you want 32 Gb/sec fibre channel adapters. It
doesn't get any faster than that. RDBMS systems are usually I/O bound,
not CPU bound. And flash is much faster variety of IO.
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
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