Re: Question: Raid vs Mirroring

From: GPOLISNE_at_DELPHI.COM <(GPOLISNE_at_DELPHI.COM)>
Date: 8 Feb 1995 21:48:54 -0500
Message-ID: <3hbvqm$e8n_at_news2.delphi.com>


robbieb_at_crl.com (Robbie Bailey) writes:

>Thomas Koithan (tkoithan_at_winternet.com) wrote:
>: BACKGROUND:
 
>: We are currently looking into the hardware needs for our HP T-500 box
>: running HPUX Release 9.04. The box will initially serve as an Oracle server
>: running the Oracle Financials package but the box will eventually serve as
>: a production box as well. We are a 24x7 company, so uptime is important. Our
>: initial user base will be about 50 growing up to 400+.
 

>: PROBLEM:
 
>: The problem that we are presently faced with is this: Do we want to go with
>: a RAID Level 5 disk array or some form of a disk mirroring system. We plan to
>: use file systems vs raw devices and our downtime window is shrinking.
 

>: QUESTION:
 
>: I am curious as to whether anyone has had any experience or preference to which
>: system would work best. My primary concern lies in terms of reliability,
>: backups, and I/O performance.
 

>: Thanks in advance for any input,
 

>: Tom Koithan, Merrill Corporation. tkoithan_at_winternet.com

RAID Level 5 is striping with parity (Level 1 is complete mirroring). RAID L5 suffers slightly on write transactions. You can potentially deploy a combination - Redo Logs, Rollback and heavy write tablespaces on RAID 1, and heavy read tablespaces such as (hopefully!) System on RAID5. Many of the vendor's Journalled File Systems (JFS in AIX, XFS in IRIX) offer performance that is well-suited for heavy database work. In the old days, and even in modern times some systems still achieve better performance using raw filesystems. While I have not experienced HP-UX on an in-depth basis, I believe they now offer a journal file system as well.

Best Regards,

George A. Polisner

>I am not current on the T500 raid offerings but the general idea is RAID
>1 for complete mirroring of your system, but it eats disk space (1 write
>to 2 disks). RAID 5 is nice for disk space but tends to be slower on
>performance and disater recovery can be a fun time when it comes to
>performance of the disk drive...
 

>Nice box though (*jealousy showing*)
>Robbie Bailey
Received on Thu Feb 09 1995 - 03:48:54 CET

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