Re: Réf. : Re: NAS, SAN or any

On Tue, 2004-07-20 at 03:32, bsimon@loxane.com wrote:
> Thanks a lot Scott.
>
> It seems that we were totally wrong when considering a network storage
> solution. I've read your techdoc
> http://techdocs.postgresql.org/guides/DiskTuningGuide and found many
> interesting remarks.
> I think that we will know focus on external Raid systems which seem to
> be relativily affordable compared to NAS or SAN (we would have had the
> budget for one of these).
> As we don't plan to have more than 5 connections (I.E process), we
> think SATA drives would fit our requirements. Could this be an issue
> for an after crash recovery ?

If you're looking at (S)ATA RAID, definitely look at escalade, as
another poster mentioned.  Last year I and a few other folks on the
lists were testing RAID controllers for survival of the power plug pull
test, and the Escalade passed (someone else did the testing, I tested
the LSI MegaRAID 320-2 controller with battery backed cache).

> We also hesitate concerning the raid level to use. We are currently
> comparing raid 1+0 and raid 5 but we have no actual idea on which one
> to use.
>
> Our priorities are :
> 1) performance
> 2) recovery
> 3) price
> 4) back-up

Basically, for a smaller number of drivers, RAID 1+0 is almost always a
win over RAID 5.  As the number of drives in the array grows, RAID 5
usually starts to pull back in the lead.  RAID 5 definitely gives you
the most storage for your dollar of any of the redundant array types.
The more important point of a RAID controller is that it have battery
backed cache to make sure that the database server isn't waiting for WAL
writes all the time.  A single port LSI Megaraid 320-1 controller is
only about $500 or less, the last time I checked (with battery backed
cache, order it WITH the battery and cache, otherwise you may have a
hard time finding the right parts later on.)  It supports hot spares for
automatic rebuild.