White paper for optimizing drives in RAID 5

[mebenz]

We have a RAID 5 array configured, but it's the minimum setup with 3 drives. Does anyone have a good link that I can download to show the increased performance by adding more drives to this array (preferably a Microsoft/HP/technet etc).

I am not a hardware person, but I need to show management that our server is not optimally configured for hard drive performance.

 

[goombawaho]

Sorry to not give you the direct answer you're looking for, but I wouldn't try to motivate management with the idea that additional hard drives will increase performance. While that may be the case (someone comment on that please), it will cost money and it will increase your usable disk capacity both of which may NOT be desired at this point in time.

In conclusion - I couldn't see the advantage of buying unneeded disk space just for a performance increase. Maybe a different disk drive configuration would be better to investigate than running RAID 5. In other words, don't try to make it into something it's not.

http://www.bytepile.com/raid_class.php#10

 

[Nelviticus]

The end of the Wikipedia page on RAID has lots of links - should be something for you there.

Nelviticus

 

[wahnula]

mebenz,

What manner of hard drive are you using? IDE? SATA? SCSI? SAS? What size?

If either IDE or SATA then petty cash can handle the addition. 500GB SATA/IDE drives are around $100 USD.

I need to show management that our server is not optimally configured for hard drive performance.

I'm a real RAID knowledge-seeker and don't honestly know that adding a fourth drive will make it more efficient, but it WILL be more economical. If X=size of drives than right now you have 3X-X or 2X worth of drive space. Provided you can add another drive to your controller without buying a new controller or drive rack, then adding another drive would give you 4X-X or 3X worth of drive space.

You could say "we spent $Y to get 2X of space, now we only need to spend $1/3Y to add 50% more space".

Another tack would be to ask for the fourth drive to configure as a hot spare, a best practice for RAID 5 arrays. This way, when the data needs are greater, the hardware would already be in place.

My seat-of-the-pants opinion as to whether it will increase speed of the array is YES for reading (more drives=less time) and NO or UNCHANGED for writing (parity overhead).

Tony

Users helping Users...

 

[goombawaho]

Good point about what kind of drive you're using. I'm always thinking in terms of enterprise size servers and thus SCSI drives which aren't cheap.

But if they were IDE or SATA, the incremental cost would not be very much compared to SCSI. And excellent point about hot spare (if supported) because things always go from bad to worse when it comes to disk drives/arrays. All those drives are spinning from the moment the array is configured, so they start to reach their MTBF at about the same time.

The other thing to always do is keep the firmware of the controller up to date along with a matching driver for the OS. Also keeping the actual hard drive firmware updated very important because I've seen IBM drive bulletins stating that certain firmwares actually caused premature drive failure and that the update was EXTREMELY critical for drive longevity. Wouldn't want to miss THAT firmware update.

 

[PRPhx]

If your looking to improve performance, AND management is willing to spend the money, you really need to be looking more at the controller your using.

Probably a fair amount of performance increase depending on what controller you use. You'll have to do some testing to really see a difference.

I will also ask, when ever do you have too much disk space??? Depending on what your doing disk space can disappear fairly quick.

Do a google search for SATA RAID 5 performance. There's a ton of info out there to look at.

 

[wahnula]

Do a google search for SATA RAID 5 performance

...we've not determined if the drives are SATA or not...nor the controller details, but I agree a dedicated card is faster...about 50% faster than an embedded SATA RAID chip. The embedded chip does not have its own RAM or CPU, and has to borrow from the system.

Tony

Users helping Users...