Yes RAID 1 is a very valid RAID level, and with the size of disks available today it can supply a useful system to a large number of organisations. My only concern with this RAID level is performance (which is not terribly good due to only 2 spindles in the system).

However, take a look at our new MAXIQ caching module. In combination with a RAID 1 it can give your webservers a ginormous kick in the pants when it comes to performance without compromising on the integrity (safety) of your data.

Ciao
Neil

All good points. Yes, having a massive cache would be nice, but there are many technical aspects that would need to be overcome, with some of those being space on the card, cost of the card once we’d done all this upgrading, speed of transfer of data to NANDflash, size of capacitor required to support this, etc etc.

So yes, a large cache would probably be a great thing but the current card design just won’t support it.

Now what we put on our future cards is totally up to our engineering teams, but I’m sure they are thinking about exactly the same valid points you make here.

Keep an eye on Adaptec’s future releases (not promising anything now )

Ciao
Neil

Let’s not tell the boss …

I have not seen statistical data that says when one drive fails they are all going to toss up their legs in the next short period of time. Use RAID 60, have at least 1 hot spare in the system.

Note that when defining a RAID 60 you can define the number of “sub-level” arrays. This means that you can determine the number of actual RAID 6’s that the RAID 60 is made of.

If you are running 96 drives and want to make one large file system, I’d recommend something like 8 sub-level RAID 6. This means that you will make up your 96 drive RAID 6 from 8 x 12-drive RAID 6’s.

This would give you 10 drives per RAID 6 usable capacity, multiplied by 8, so 80 drives usable capacity. You can work that out for whatever size drive you are using.

Note that this will be one very fast and large RAID config. Of course you might want to make multiple RAID configs depending on your OS environment, and that there are many, many variables you can do here.

Good luck and keep us in the loop on your progress.

Ciao
Neil

What I want to tell him, is that with raid-10 we have, say, 1% chance per year of losing the array. While with raid 60 it’s down to 0.1% but we lose 30% performance. I can use MTBF/AFR to calculate the MTTDL, but I’m getting paranoid about all the talks of correlated failures. Listening to everyone’s anecdotes on the net, it sounds like all drives will fail quickly after the first failure. Is there a rule of thumb ? Like 2x or 100x the AFR after the first failure ?

Thanks,

p.s. : My 8 drives above was an example. The array I’m planning is a 96 drives SAS, so it’ll be raid-60. Actually it will possibly be a raid 600, with 2 controllers in software raid-0. I need every ounce of performance I can get without sacrificing reliability (our access patterns are not the usual file server). Falling back to raid-10 will be a last resort if I can’t tweak raid-6 to have adequate performance.