-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
david@xxxxxxx wrote:
> On Fri, 7 Sep 2007, Tobias Brox wrote:
>
>> We're also considering to install postgres on SAN - that is, my boss is
>> convinced this is the right way to go.
>>
>> Advantages:
>>
>> 1. Higher I/O (at least the salesman claims so)
>
In general a SAN does not provide more I/O than direct attached storage.
It is all about the BUS, Controller and drive types.
> only if you buy better disks for the SAN then for the local system (note
> that this includes battery backed ram for write caching. the SAN will
> include a bunch becouse it's performance would _suck_ otherwise. if you
> don't put any on your stand-alone system you are comparing apples to
> oranges)
>
>> 2. Easier to upgrade the disk capacity
>
> only if you buy a SAN with a lot of empty drive slots, but wouldn't buy
> a system with empty drive slots.
Well there are SANs that have trays that can be stacked, but then again
you can get the same thing with DAS too.
>
>> 3. Easy to set up "warm standby" functionality. (Then again, if the
>> postgres server fails miserably, it's likely to be due to a disk
>> crash).
>
>> Also, my boss states that "all big enterprises uses SAN nowadays".
>
Uhmm as someone who consults with many of the big enterprises that are
running PostgreSQL, that is *not* true.
>> 2. Expensive
>
> no, _extremely expensive. price one and then look at how much hardware
Let me just +1 this. The amount of DAS storage you can get for 30k is
amazing compared to the amount of SAN you can get for 30k.
Joshua D. Drake
> you could buy instead. you can probably buy much mroe storage, and a
> couple complete spare systems (do replication to a local spare as well
> as your remote system) and end up with even more reliability.
>
>> 3. "Single point of failure" ... but that you have either it's a SAN or
>> a local disk, one will anyway need good backup systems (and eventually
>> "warm standby"-servers running from physically separated disks).
>
> no, with local disks you can afford to have multiple systems so that you
> don't have a SPOF
>
>> 4. More complex setup?
>>
>> 5. If there are several hosts with write permission towards the same
>> disk, I can imagine the risks being higher for data integrity
>> breakages. Particularly, I can imagine that if two postgres instances
>> is started up towards the same disk (due to some sysadmin mistake), it
>> could be disasterous.
>
> when you are useing a SAN for a database the SAN vendor will have you
> allocate complete disks to each box, so you don't have multiple boxes
> hitting the same drive, but you also don't get a lot of the anvantages
> the salesman talks about.
>
> David Lang
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>
- --
=== The PostgreSQL Company: Command Prompt, Inc. ===
Sales/Support: +1.503.667.4564 24x7/Emergency: +1.800.492.2240
PostgreSQL solutions since 1997 http://www.commandprompt.com/
UNIQUE NOT NULL
Donate to the PostgreSQL Project: http://www.postgresql.org/about/donate
PostgreSQL Replication: http://www.commandprompt.com/products/
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iD8DBQFG4b9/ATb/zqfZUUQRAnBiAJ4kdOicN3If4scLAVdaU4nS+srGHQCgnkR2
C6RvSyLcAtgQ1bJJEau8s00=
=lqbw
-----END PGP SIGNATURE-----
---------------------------(end of broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings
