Re: Fwd: RE: RAID or NOT to RAID?

From: Eric D. Pierce <PierceED_at_csus.edu>
Date: Thu, 09 Aug 2001 15:31:45 -0700
Message-ID: <F001.0036662C.20010809141640@fatcity.com>

(Please critique the following)

NT/Win2k RAID background:

http://www.ultratech-llc.com/KB/?File=RAID.TXT

(linked from http://www.ultratech-llc.com/KB/?File=!Contents.TXT )

---excerpt---

...

DATABASE TYPE SERVER ........... assuming 6-10 drives total

{Low Space Requirements or Small Footprint}

2 x 9GB (or 18GB) ----- RAID1 (OS and pagefile)
2 x 18GB (or 36GB) ----- RAID1 (Database Logs)
2 x 18GB (or 36GB) ----- RAID1 (Databases)

{More Space Redundancy}

2 x 9GB (or 18GB) ----- RAID1 (OS and pagefile)
2 x 18GB (or 36GB) ----- RAID1 (Database Logs)
6 x 18GB (or 36GB) ----- RAID5 (Databases)

{More Redundancy}

2 x 9GB (or 18GB) ----- RAID1 (OS and pagefile)
2 x 18GB (or 36GB) ----- RAID1 (Database Logs)
5 x 18GB (or 36GB) ----- RAID5 (Databases)
1 x 18GB (or 36GB) ----- Hot Spare

{Redundancy and Performance}

2 x 9GB (or 18GB) ----- RAID1 (OS and pagefile)
2 x 18GB (or 36GB) ----- RAID1 (Database Logs)
6 x 18GB (or 36GB) ----- RAID10 (Databases)

Additionally, it is best to **AVOID** the following practices:

Putting the pagefile on RAID5
Putting the pagefile on a separate PARTITION, but not separate DISK
Making logical partitions out of a single, huge RAID5
Putting the pagefile on a non-redundant drive.

In order of preference, the pagefile should go here:

Across multiple, non-busy drives (not just different partitions)
On its very own dedicated drive (with redundancy)
On a non-busy drive where %SystemRoot% does NOT reside
On the same drive and partition as %SystemRoot%

Always ensure that your pagefile is on some sort of RAID drive, as you will lose your whole system if the pagefile becomes unavailable. Thus, even though it is performance draining and wasteful, having your pagefile on a RAID5 partition would still be better than having it on a single drive (with regards to uptime and redundancy).

These are the guidelines I try to follow regarding the optimal drive configuration (performance and recoverability) on NT systems.

To support more esoteric configurations or a different number of drives, adjust your RAID choices accordingly...

NOTE: If you are lucky enough to find 4GB drives, use them for the OS, but you'll probably be stuck with 9s...

PERSONAL NOTES

ATA RAID is gaining some serious momentum. I'm using it at home, and it performs better than advertised. I'm still not at the level where I would consider it appropriate for Mission Critical servers. Home, Development and extremely low-budget environments are good candidates, but I am still of the mind that SERVER = SCSI. On the desktop, the cost and size of ATA drives are considerable advantages for almost every situation (multimedia aside).
3Ware makes some awesome, ATA RAID controllers, supporting up to 8 drives, and various RAID configs. Their benchmarks must be seen to be believed.
AVOID SOFTWARE RAID LIKE THE PLAGUE. It is less flexible than Hardware RAID, requires more CPU cycles to operate, and the lack of any hotswap capabilities means that you will likely suffer downtime to correct a failed drive, even if your system doesn't immediately crash and burn.

Additionally, the RAID configuration is stored in the registry, which means that if the OS goes, you're basically looking at restoring from tape...

There is a subtle difference between RAID0+1 and RAID10 that should not be overlooked. In all likelihood, it is the latter that you want, not the former.

RELATED TOPICS (ALSO IN THIS ARCHIVE)

KEYWORDS: PAGEFILE, PERFORMANCE, CONFIGURATION, SETUP, RAID, HOTSPARE, MIRROR, ARRAY, DISKS, FAULT TOLERANT, FAULT TOLERANCE To mail this document to someone, click HERE.

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Author: Eric D. Pierce
  INET: PierceED_at_csus.edu

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Received on Thu Aug 09 2001 - 17:31:45 CDT