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From: "Matt Casters" <Matt(dot)Casters(at)advalvas(dot)be>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: Re:
Date: 2005-01-20 21:39:02
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance

Actually that's a great idea!
I'll have to check if Solaris wants to play ball though.
We'll have to see as we don't have the new disks yet, ETA is next week.



-----Oorspronkelijk bericht-----
Van: Joshua D. Drake [mailto:jd(at)commandprompt(dot)com] 
Verzonden: donderdag 20 januari 2005 21:26
Aan: matt(dot)casters(at)advalvas(dot)be
CC: pgsql-performance(at)postgresql(dot)org
Onderwerp: Re: [PERFORM]

Matt Casters wrote:
> Thanks Stephen,
> My main concern is to get as much read performance on the disks as 
> possible on this given system.  CPU is rarely a problem on a typical 
> data warehouse system, this one's not any different.
> We basically have 2 RAID5 disk sets (300Gb) and 150Gb) with a third 
> one coming along.(around 350Gb)

Why not run two raid systems. A RAID 1 for your OS and a RAID 10 for your
database? Push all of your extra drives into the RAID 10.


Joshua D. Drake

> I was kind of hoping that the new PGSQL tablespaces would allow me to 
> create a storage container spanning multiple file-systems, but 
> unfortunately, that seems to be not the case.  Is this correct?
> That tells me that I probably need to do a full reconfiguration of the 
> disks on the Solaris level to get maximum performance out of the system.
> Mmmm. This is going to be a though one to crack.  Perhaps it will be 
> possible to get some extra juice out of placing the indexes on the 
> smaller disks (150G) and the data on the bigger ones?
> Thanks!
> Matt
> -----Oorspronkelijk bericht-----
> Van: Stephen Frost [mailto:sfrost(at)snowman(dot)net]
> Verzonden: donderdag 20 januari 2005 15:26
> Aan: Matt Casters
> CC: pgsql-performance(at)postgresql(dot)org
> Onderwerp: Re: [PERFORM]
> * Matt Casters (Matt(dot)Casters(at)advalvas(dot)be) wrote:
>>I have the go ahead of a customer to do some testing on Postgresql in 
>>a couple of weeks as a replacement for Oracle.
>>The reason for the test is that the number of users of the warehouse 
>>is going to increase and this will have a serious impact on licencing 
>>costs. (I bet that sounds familiar)
> Rather familiar, yes... :)
>>We're running a medium sized data warehouse on a Solaris box (4CPU, 
> RAM) on Oracle.
>>Basically we have 2 large fact tables to deal with: one going for 400M 
>>rows, the other will be hitting 1B rows soon.
>>(around 250Gb of data)
> Quite a bit of data.  There's one big thing to note here I think- 
> Postgres will not take advantage of multiple CPUs for a given query,
Oracle will.
> So, it depends on your workload as to how that may impact you.  
> Situations where this will be unlikely to affect you:
> Your main bottle-neck is IO/disk and not CPU.
> You run multiple queries in parallel frequently.
> There are other processes on the system which chew up CPU time anyway.
> Situations where you're likely to be affected would be:
> You periodically run one big query.
> You run a set of queries in sequential order.
>>My questions to the list are: has this sort of thing been attempted 
>>before? If so, what where the performance results compared to Oracle?
> I'm pretty sure it's been attempted before but unfortunately I don't 
> have any numbers on it myself.  My data sets aren't that large (couple 
> million
> rows) but I've found PostgreSQL at least as fast as Oracle for what we 
> do, and much easier to work with.
>>I've been reading up on partitioned tabes on pgsql, will the 
>>performance benefit will be comparable to Oracle partitioned tables?
> In this case I would think so, except that PostgreSQL still won't use 
> multiple CPUs for a given query, even against partitioned tables, aiui.
>>What are the gotchas?
> See above? :)  Other issues are things having to do w/ your specific
> SQL- Oracle's old join syntax isn't supported by PostgreSQL (what is 
> it, something like select x,y from a,b where x=%y; to do a right-join,
>>Should I be testing on 8 or the 7 version?
> Now that 8.0 is out I'd say probably test with that and just watch for 
> 8.0.x releases before you go production, if you have time before you 
> have to go into production with the new solution (sounds like you do- 
> changing databases takes time anyway).
>>Thanks in advance for any help you may have, I'll do my best to keep 
>>pgsql-performance up to date on the results.
> Hope that helps.  Others on here will correct me if I misspoke. :)
> 	Stephen
> ---------------------------(end of 
> broadcast)---------------------------
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