>Can anyone please comment on the use of RAID in an Oracle OLTP database configuration,
>specifically with storage on a Hitachi 9900 serious storage system? The Hitachi and Sun
>people that I have spoken with so far would have me believe that I can put my entire Oracle
>database on a Hitachi 9900 using all RAID-5 -- because the RAID-5 on this box is so fast and
>has so much cache, etc., etc...
>Anyway, I'm not convinced that any of the people I've spoken with know a thing about Oracle,
>and despite the fact that I've asked them over and over for some specific real-world examples
>of Oracle configurations with the 9900 series... So far, I've seen nothing.
>Everything I've seen and heard tells me that RAID-5 should be avoided, for the most part --
>and that an entire Oracle database should most definitely NOT be put all on RAID-5. The
>Hitachi 9900 also supports RAID1+0. I desperately want to hear from anyone who has some
>real-world experience with this hardware, with Oracle.
Your apprehension about RAID 5 is understandable; especially
considering its long-standing, and well-known performance limitations.
However cache centric arrays like the HDS 99xx don't behave or perform
like a traditional array. You will be happily surprised by Oracle's
performance on these boxes running RAID 5. Switching to RAID 1 or 1+0
will simply be a waste of disk capacity. As for suggestions for best
performance on these arrays...
-Follow best practices for Oracle, especially the use of multiple
table spaces, ie. make your DB modular vs monolithic
-Keep your primary index small(ish) to give your self the option of
locking it into cache (ala FlashAccess) for solid state disk like
-Keep or move "hot" table spaces to under utilized back-end array
controllers (ACP pairs). HDS has utilities to help you identify and
move LUNs as needed.
-Think of, and treat, each ACP pair as if it were a separate disk
-Use VxVM DPM, or the like, to trunk multiple FC HBAs together to form
a fat pipe and stripe across multiple LUNs controlled by multiple ACP
Some of the old rules simply don't apply with these arrays because
they are not like other arrays. My first experience with this disk
type in an open systems environment was with an HDS 7700E. Like the
99xx series after it, this array has separate data and command paths,
which I think is a major factor in their surprising OLTP performance.
A muli-Kbyte data block doesn't have to compete with a multi-byte
command for transportation. Personally I think this is a huge and
under recognized feature.