Topic: RAID for SME 6.0beta2

[Kelvin]

>Only use RAID0 when your data is worthless. Only use RAID5 (software) when
>your CPU/performance is worthless.

Ho ! Ho ! Yes, I remember that post ...

Kelvin

[Brent]

Okay.... now you've confused the newbie!!!

So a RAID 5 via software can hurt performance... but a RAID 5 via hardware does not?  Is that what I'm to gather from this?  I knew that a RAID 1 array and RAID 0 were not was I was looking for.  I was hoping to have a system that would spread the data over multiple drives to give me some redundancy and to reduce the need to backup my data to another media, but I also wanted one that would allow me to replace a failing drive without the need to completely rebuild things.  So was a RAID 5 the best choice?

Also, I've discovered that I cannot use my Smart Array 221 without purchasing a copy of Compaq's SmartStart 5.5 CD - a $21 value that costs $20 to ship to Canada regular post!!  Such is the pennance of one who buys second-hand hardware.

if (installation_disks == none)
     { additional purchases = many && setup = hard
     } else { setup = easy }

[Kelvin]

Brent,

>So a RAID 5 via software can hurt performance... but a RAID 5 via hardware does
>not?

Mostly correct. How much performance is impacted / improved by Hardware RAID 5 depends on the controller you use. Believe me, if you go by the marketing blurbs from the established RAID card manufacturers, one can be forgiven for thinking they can make you breakfast !

>reduce the need to backup my data to another media

Reduce = yes
replace = no

If you deleted an important file that you need, RAID anything doesn't help you. Backups do (provided they work of course ! )

>wanted one that would allow me to replace a failing drive without the need to
>completely rebuild things

That's one of the basic ideas behind RAID.

>So was a RAID 5 the best choice?

RAID 5's advantages / disadvantages over RAID 1 are :-
1. Higher number of drives used, so you are spreading your risk over a larger number of drives.
2. Higher number of drives used, so it costs more !
3. Higher read performance, each drive can read data independently (ie. in a 3 drive array, all 3 drives can read simultaneously and present the data to the controller to reassemble and submit to the computer).
4. Writes are more complicated and slightly slower - hence the use of cache RAM on most RAID cards to address this.
5. The cache also helps with data access as well
and more, but you get the picture.

Aside from RAID 5, you can also get a performace boost by employing RAID 0+1 in hardware which is a mirrored stripe set.

RAID-0 (stripe set) basically spreads your data across 2 drives (thereby *increasing* your data risk) to improve performance as each of the 2 drives write or read only half of the required data and they do it simultaneously. RAID-1 is a mirrored set as we know. The idea is to combine the 2, so that the stripe set is mirrored. There are discussion papers out there which says that RAID 1+0 is in fact better than RAID 0+1 but it is harder to find controllers that will do 1+0.

Between RAID 1 and RAID 5, RAID 1 has greater cost per megabyte of storage.

>Also, I've discovered that I cannot use my Smart Array 221 without purchasing a
>copy of Compaq's SmartStart 5.5 CD

I have not tried this myself but ever thought of using a 3rd party controller (Mylex, 3ware, etc ?). Some of these cards have on board BIOS to create the drive packs and even if they did not, most have downloadable drivers / utilites.

Kelvin

[James Pybus]

Try asking about on news groups relating to the compaq server / conroller card you use to see if anyone has a cd they could copy for you, they can often be very helpful, or try emule etc.

HTH

[Brent]

Kelvin & James,

Thanks to both for your suggestions.  However, I already have my Smart Array 221 and have ordered the CD from Compaq, so the money's been spent.  My smartest move is to follow through instead of spending more money trying to save money I already spent.  Does that make sense?

I think the RAID 5 was a wise choice, all in all.  I still plan on configuring regular data backups using SME's Backup to Workstation feature, dumping a copy of critical files to my other server for archiving via CD.

Now I just have to wait for the SmartStart CD to arrive so I can begin configuring this machine and get it running.  Then comes the fun part - the database programming!!