Advice: HA Storage Appliance for Postgres

[John Martinez]

On Aug 15, 2005, at 4:44 PM, Danny Howard wrote:



> ...
>
> Can someone offer a bit of advice here:
> - Am I thinking the right way?
>
>

Somewhat, although I would avoid using SCSI in preference to Fibre  
Channel, that is if you want to connect multiple hosts to the same  
array.



> - I think I want to avoid anything called "SAN" right?
>
>

Note necessarily. But just because I say "Fibre Channel", doesn't  
mean I'm saying SAN. You can direct-attach Fibre Channel devices to  
your host if you have Fibre Channel HBAs. If you want to connect  
multiple hosts, a SAN is the easiest way to do so, but can get  
expensive In the end, your host will see these drives as SCSI.  
Confused yet? Don't worry, I was somewhat confused at first, too.



> - These days, is SATA versus SCSI versus fiber versus copper connects
>   important?
>
>

You're mixing several things together. SATA versus SCSI are drive  
types. Fiber Channel drives are a third type of drive, having nothing  
to do with fiber optic cables (yet). You can find arrays with the  
three types of drives that have fiber connections (most common) and  
some that have copper connections.

There are lots of high-performance SATA disks out there now, with  
comparable performance to SCSI and Fibre Channel. Although be careful  
of write performance. Once you pick some vendors to look at, see  
about what tests they've done given typical RAID set ups. Even go so  
far as requesting an evaluation unit and do your own testing.



> - Anyone have a particular vendor they like?  There was a place in
>   Soquel that was very helpful for me back in 2000 but I can not  
> seem to
>   find them any more ... HP?  IBM?  Sun?  A local integrator?  (ASA
>   don't seem to do this stuff.)
>
>

Depends on your budget. These things can get pretty expensive. We  
tend to gravitate towards Hitachi.



> - Is an NFS/NetApp solution viable?
>
>

Depends on what you're trying to do. Some people like to use NFS  
(NetApp) for database hosting, I personally don't like NFS for that  
type of application, but it is easy to set up. From what I  
understand, you can get a NetApp with Fibre Channel interfaces now  
and use it like a Fibre Channel array.



> - Do smaller disks provide better performance in RAID contexts?
>
>

That's the thought, anyway. I find that the number of spindles has  
more to do with performance (most Fibre Channel disks being 10k and  
15k RPM), although you have to be careful of the reliability factor  
with too many spindles in your RAID set.

The issue you may run into is support for your OS. I don't use  
FreeBSD for high-end storage (we use Solaris). You'll find things get  
complicated with multipathing and how to handle that on your OS.  
Storage vendors can get picky at that point. I'm not saying that  
vendors won't support FreeBSD. I'm just saying we found Solaris to be  
traditionally better supported, although Linux is just as supported  
these days.

Good luck,
-john