Re: st: re: Memory, Stata 10, and 32-bit XP

[Phil Schumm <pschumm@uchicago.edu>]

On Feb 22, 2008, at 11:01 AM, Fred Wolfe wrote:
> Our group is switching over to the Power Mac for some of the  
> reasons enumerated by Kit. We are wondering if Kit (and others)  
> have experience with the extent to which performance is boosted (+  
> or -0) by Raid 0, 1 or 5) using Stata, and if there are any  
> recommendations.

I assume you're not talking about a Power Mac (PowerPC-based macs are  
no longer made), but rather one of the current offerings (i.e., Mac  
Pro or Intel-based Xserve).  At the risk of giving a naive answer,  
let me point out that RAID 0 (striped) can improve read and write  
performance, RAID 1 (mirrored) can provide limited increased read  
performance (but only if the OS supports it) at the cost of a small  
reduction in write performance, and RAID 5 (striped, parity  
distributed over multiple disks) provides improved read and write  
performance.  RAID 1 and 5 are robust to the failure of one of the  
disks, while RAID 0 is not.

Note that software RAID is not the same as hardware RAID; the former  
is not as robust nor will you see as much of a performance increase.   
OS X is capable of RAID 0 or 1 by itself (i.e., software RAID), if  
you have the disks available.  We use software RAID 1 (mirrored) on  
our Xserves for redundancy, and it has worked well for us in the  
past.  However, it is not comparable to a true hardware RAID.

Since Stata does so much in memory, I think the impact of RAID on  
Stata use will depend pretty heavily on what you are doing.  If  
you're doing a lot of reading and writing from disk, then you should  
expect to see some performance benefit *if* you have a RAID  
implementation that can provide it.  If not, then you won't.

Perhaps you knew all this already.  If so, I'm afraid I have no  
experience in running OS X with a true hardware RAID, much less in  
using Stata on such a machine.


-- Phil

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