Performance isue in VA and big raid-groups?

[Jorgen Ekholm]

Hi!

I'm conserned about the VA and big RAID-groups, how is data written to disk? In an XP my understanding is that there is a function called "gathering write" which makes several write IO in the fron end to a few on the back end.

Is there a similar function in the Virtual Array or do you always write the data directly and get a big penalty because you have so many disks in the arraygroup?

//Jorgen Ekholm, Telia

[Vincent Fleming]

Why are you concerned about performance? Are you having a problem with a VA? The one I tested delivered impressive performance.

I don't know if it has write-gathering cache, but with 1GB per controller and the performance I saw, I suspect it does. Besides, write-gathering cache is no longer a new idea, and I just assume that any controller designed in the last 5 years has it.

[Jorgen Ekholm]

Hi!

I don't have any VA today, but I realy need to be sure about it's performance. Big RAID-grous is one issue that I'm concerned with. If anyone have done some testing, please feel free to share it with me.

//Jorgen

[David Navarro]

Hi, Jorgen!
I Haven't tested any VA yet! But I have a file that shows what performance can you expect in VA7100 configured in 0+1. I don't know if it can help you. But I hope so.

[Vincent Fleming]

So, you must be a DBA. :-)

The real difference with a VA is that you are letting the RAID unit do the striping, rather than doing it manually from the host. In a general sense, striping a large RAID group will only increase your performance, as it balances the load over multiple drives automatically.

This type of device can perform really well for most applications. You sound (from your tone) unsure that you can tweak the performance you need out of a VA... which could be true - but most applications will run just fine on a VA-class storage device. If you need real extreme performance (let's face it, 99.999% of the systems out there don't), you can do two things - add more drives the the VA [over-engineer it], or get something like an XP.

Good luck

[Vincent Fleming]

Jorgen,

I found the attached white paper on VA7100 performance, and thought you might be interested.