Message-ID: <4E206D55.2090805@missouri.edu>
Date: Fri, 15 Jul 2011 11:39:49 -0500
From: Robert Schnabel <schnabelr@missouri.edu>
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To: Greg Smith <greg@2ndquadrant.com>
CC: chris <chricki@gmx.net>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Hardware advice for scalable warehouse db
References: <ivon1e$81d$1@dough.gmane.org> <4E1FE7ED.90909@2ndquadrant.com>
In-Reply-To: <4E1FE7ED.90909@2ndquadrant.com>
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On 7/15/2011 2:10 AM, Greg Smith wrote:
> chris wrote:
>> My employer is a university with little funds and we have to find a
>> cheap way to scale for the next 3 years, so the SAN seems a good chance
>> to us.
> A SAN is rarely ever the cheapest way to scale anything; you're paying
> extra for reliability instead.
>
>
>> I was thinking to put the WAL and the indexes on the local disks, and
>> the rest on the SAN. If funds allow, we might downgrade the disks to
>> SATA and add a 50 GB SATA SSD for the WAL (SAS/SATA mixup not possible).
>>
> If you want to keep the bulk of the data on the SAN, this is a
> reasonable way to go, performance-wise.  But be aware that losing the
> WAL means your database is likely corrupted.  That means that much of
> the reliability benefit of the SAN is lost in this configuration.
>
>
>> Any experiences with iSCSI vs. Fibre
>> Channel for SANs and PostgreSQL? If the SAN setup sucks, do you see a
>> cheap alternative how to connect as many as 16 x 2TB disks as DAS?
>>
> I've never heard anyone recommend iSCSI if you care at all about
> performance, while FC works fine for this sort of job.  The physical
> dimensions of 3.5" drives makes getting 16 of them in one reasonably
> sized enclosure normally just out of reach.  But a Dell PowerVault
> MD1000 will give you 15 x 2TB as inexpensively as possible in a single
> 3U space (well, as cheaply as you want to go--you might build your own
> giant box cheaper but I wouldn't recommend ).

I'm curious what people think of these:
http://www.pc-pitstop.com/sas_cables_enclosures/scsase166g.asp

I currently have my database on two of these and for my purpose they 
seem to be fine and are quite a bit less expensive than the Dell 
MD1000.  I actually have three more of the 3G versions with expanders 
for mass storage arrays (RAID0) and haven't had any issues with them in 
the three years I've had them.

Bob