Re: Postgres for a "data warehouse", 5-10 TB

On 09/11/2011 09:21 AM, Igor Chudov wrote:
>
>
> On Sun, Sep 11, 2011 at 9:16 AM, Claudio Freire <klaussfreire(at)gmail(dot)com <mailto:klaussfreire(at)gmail(dot)com>> wrote:
>
> On Sun, Sep 11, 2011 at 3:59 PM, Igor Chudov <ichudov(at)gmail(dot)com <mailto:ichudov(at)gmail(dot)com>> wrote:
> > Well, right now, my server has twelve 7,200 RPM 2TB hard drives in a RAID-6
> > configuration.
> > They are managed by a 3WARE 9750 RAID CARD.
> >
> > I would say that I am not very concerned with linear relationship of read
> > speed to disk speed. If that stuff is somewhat slow, it is OK with me.
>
> With Raid 6 you'll have abysmal performance on write operations.
> In data warehousing, there's lots of writes to temporary files, for
> sorting and stuff like that.
>
> You should either migrate to raid 10, or set up a separate array for
> temporary files, perhaps raid 0.
>
>
> Thanks. I will rebuild the RAID array early next week and I will see if I have a Raid 10 option with that card.
>
> Quantitatively, what would you say is the write speed difference between RAID 10 and RAID 6?
>

Note that using RAID 10, while faster, cuts your usable space in half. 12 2TB drives in raid 10 == 6 drives * 2TB == 12 TB total space. That's not big enough, is it?

-Andy