Re: Raid devices on NT

johnj_at_dbbasics.com wrote:
>
> Does anybody know the pros and cons of using RAID 5 devices on
> NT servers. I come from the old school of Oracle that says for
> best performance and recoverability, spread your datafiles and
> system files across as many disk as possible. The more the
> better. Well, now with Oracle residing on NT servers and using
> RAID 5, I am seeing setups that have one (1) disk that has the
> NT system on it, and then 5 disk setup in RAID 5. Basically
> the RAID 5 treats it as one big disk and the stripping across
> disk is handled by the operating system. And to top that
> the system disk are usually too small to even put the Oracle
> system files on that disk. I am left with putting ALL of Oracle
> on one big RAID 5 disk. Let me hear the pros and cons guys
> and gals. Post back here or e-mail to johnj_at_dbbasics.com.
> Thanks.
>
> John Jones
> DB Basiscs.com
> http:\\www.dbbasics.com

John,
Let me give you my 2 cents worth. Most database management systems have two general categories of read/write activity:

1 - Random read/write. Where the work is really done on inserts, updates, deletes and even selects.

2 - Sequential write. Data is first written to the transaction log, then the database engine will take data written to the log and write it back to the database.

This activity is present on any database type system. These can include Oracle, Sybase, MS-SQL Server, Informix, MS Exchange (it is a database after all), journaled Unix file systems (AIX).

You need to look at how to get the best performance while still having resiliency to failure. From my perspective I generally recommend that people go with the following:

A RAID 5 stripe set for the random read/write activity. This will give you the greatest storage capability. Remember RAID 5 net storage is N-1, where N is the number of members in the RAID set.

A RAID 1 mirror set for the sequential write activity. This will give you the fastest write performance and still give you resiliency in case of failure. RAID 5 has a write performance penalty (outside of the scope of this brief note). Transaction logs are small in comparison to the size of the data that they "cover". I would probably put the OS and paging file on this device as well.

Hardware RAID should be implemented, not Windows NT software based RAID.

I hope that this helps.

Bill Riedy
(written from my wife's ISP account) Received on Sun Nov 23 1997 - 00:00:00 CET