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Re: SAN vs Internal Disks

From: "Harsh Azad" <harsh(dot)azad(at)gmail(dot)com>
To: "david(at)lang(dot)hm" <david(at)lang(dot)hm>
Cc: Decibel! <decibel(at)decibel(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: SAN vs Internal Disks
Date: 2007-09-12 05:44:27
Message-ID: a199704d0709112244j2ebe5f6cpfd36a4c9e81e2aee@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Yeah, the DAS we are considering is Dell MD3000, it has redundant hot
swappable raid controllers in active-active mode. Provision for hot spare
hard-disk. And it can take upto 15 disks in 3U, you can attach two more
MD1000 to it, giving a total of 45 disks in total.

-- Harsh

On 9/12/07, david(at)lang(dot)hm <david(at)lang(dot)hm> wrote:
>
> On Tue, 11 Sep 2007, Decibel! wrote:
>
> > On Tue, Sep 11, 2007 at 05:09:00PM -0400, Michael Stone wrote:
> >> On Tue, Sep 11, 2007 at 03:55:51PM -0500, Decibel! wrote:
> >>> Also, to reply to someone else's email... there is one big reason to
> use
> >>> a SAN over direct storage: you can do HA that results in 0 data loss.
> >>> Good SANs are engineered to be highly redundant, with multiple
> >>> controllers, PSUs, etc, so that the odds of losing the SAN itself are
> >>> very, very low. The same isn't true with DAS.
> >>
> >> You can get DAS arrays with multiple controllers, PSUs, etc.  DAS !=
> >> single disk.
> >
> > It's still in the same chassis, though, which means if you lose memory
> > or mobo you're still screwed. In a SAN setup for redundancy, there's
> > very little in the way of a single point of failure; generally only the
> > backplane, and because there's very little that's on there it's
> > extremely rare for one to fail.
>
> not nessasarily. direct attached doesn't mean in the same chassis,
> external drive shelves attached via SCSI are still DAS
>
> you can even have DAS attached to a pair of machines, with the second box
> configured to mount the drives only if the first one dies.
>
> David Lang
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>



-- 
Harsh Azad
=======================
Harsh(dot)Azad(at)gmail(dot)com

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