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Disk Arrays

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Karen Benner
Occasional Contributor

Disk Arrays

How do you decide which disk array is best for your needs? We are considering an N4000/4 with 5G RAM and we need 400G of disk space for an Oracle 7.3.4 Data Base and Oracle Apps 10.7
5 REPLIES
Vincent Fleming
Honored Contributor
Solution

Re: Disk Arrays

Oh boy, that's a big question!

There are several things to consider when picking out a disk array... some may apply to you and some may not. Also the order of importance will be very individual to you, and will determine which type of product you will end up with.

There are 3 types of storage out there today. Low-end, Midrange, and Enterprise. Low-end would be JBOD, midrange would be VA 7100, VA 7400, FC60, etc., and Enterprise would be XP512 or EMC.

Some attributes of these three:
Low-end: cheap, unreliable, poor performance
Mid-range: reasonable cost, good reliability, good performance
Enterprise: high cost, very reliable, great performance

Here's the basics for picking what you need and can have:

1. Tolerance for system outages
If you can live with being down a couple of hours every few months or so, you can use JBOD. If you cannot every be offline (ie: online trading of securities), you better be sure to get Enterprise Storage (XP48 or XP512). If you're somewhere inbetween the two (most are), then you have choices. You can get a midrange, fault-tolerant array, such as the VA 7100 or VA 7400.

2. Performance requirements
If you require very high performance, then you want something with a LOT of cache. For example, the XP512 can hold 32GB of cache, and has up to 32 Fibre Channel ports (aggregate bandwidth of up to 3.2GB/s). You may also need to purchase many more drives than you think as well - more drives = more performance.
(You can expect the average drive to produce somewhere between 100-150 I/O's per second - size your array accordingly.) If your performance needs are modest, the VA series may be adequate for your performance needs, at a more attractive price.

3. Budget
Most people like to think that money is no object, but most of the time it is. If money is truely no object, but an XP512 - your performance will be the best it can get, and it's fully fault tolerant. Expensive compared to midrange and low end storage, but a great gadget. If you're at the other end of the spectrum, you may be forced to buy JBOD and live with things like downtime and poor performance. If, like most, you're somewhere in between, there's that mid-range storage again.

Now, when shopping, be prepared. Know what your performance requirements are (look at your current system performance, and make an educated guess where you want the new one to be. ie: current database is percieved as slow. You're doing 2000 IOPS to the drives. You guess that 4000 IOPS should do it. You'll need 30-40 drives to get that performance. You need 400GB... 400GB/40 drives = 10GB/drive. You can live with small drives, (the smallest is usually 18GB now). From there, you figure from budget what you can afford. If you have >$250,000 (with the above config), you should be able to get an XP512 or similar, otherwise, you're getting mid-range storage like the VA series.

The important thing to note here is that you first make sure the disk unit meets your needs, then think about price.

Good luck, and happy buying!
No matter where you go, there you are.
A. Clay Stephenson
Acclaimed Contributor

Re: Disk Arrays

Hi Karen:

I would start by examining this site:
http://www.hp.com/products1/storage/disk_arrays/index.html

I'm surprised that you are looking at the obsolete version of Oracle.

I would think a couple of VA7100's or a VA7400 would nicely fit your requirements. I would certainly buy more capacity than you think you need; it's easier to get it now than to have to go back to the well. I think this would give you the most bang for the buck.

With ~400GB's I would also consider a pair of Model 12H's fully populated with 36GB drives. You would need to keep each of these at about 50% of capacity and carefully configure your volume groups and logical volumes to get good performance. This nice thing about these arrays is the ease of maintenance. The performance is a bit poorer but the array maintenance is nothing more than
see bad disk, replace bad disk, walk away.

You probably also need to look at a DLT library for backup.

My 2 cents, Clay
If it ain't broke, I can fix that.
paul courry
Honored Contributor

Re: Disk Arrays

I don't know about the disk array, but if you are planning on 400Gb of disc, cram every bit of RAM you can into that box.

Make the first slot HP RAM for the sake of your maintenance contract and fill the rest with 3rd party RAM from a reputable vendor such as Strategic Memory Solutions
A. Clay Stephenson
Acclaimed Contributor

Re: Disk Arrays

Hi Karen:

I've had one other thought I think I'll share. Of far more importance than the choice of disk array is the quality/efficiency of your code. I've seen many,many instances of poor performance that no amount of hardware, database tuning, kernel tuning would significantly improve but that small changes in the code would result in a 10X or greater performance boost.

The good news is that nowadays a 400GB database is not considered large (unless you have many,many small rowa) so that a low/mid-range solution should work just fine but, if and only if, your code is efficient. If not, you could throw a SuperDome and an XP512 or EMC array at it and still have a dog.

If this is a high-availabilty application then you should also consider implementing MC/ServiceGuard (if your budget permits).

Food for thought, Clay

If it ain't broke, I can fix that.
Andrew R.
Advisor

Re: Disk Arrays

I would consider xp48 and install disk Raid 5 . Raid 5 on the xp are very close in performance to Raid 1 and much cheaper. The xp is very reliable,fast and you'll have room to expand in the future (think about tomorrow). I will also recommend buying an "L" class and implement Service Guard.

Good Luck
Live for the infinity life