| From: | Laszlo Nagy <gandalf(at)shopzeus(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: SSD + RAID |
| Date: | 2009-11-15 02:09:51 |
| Message-ID: | 4AFF62EF.3090201@shopzeus.com |
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| Lists: | pgsql-performance |
Robert Haas wrote:
> 2009/11/14 Laszlo Nagy <gandalf(at)shopzeus(dot)com>:
>
>> 32GB is for one table only. This server runs other applications, and you
>> need to leave space for sort memory, shared buffers etc. Buying 128GB memory
>> would solve the problem, maybe... but it is too expensive. And it is not
>> safe. Power out -> data loss.
>>
I'm sorry I though he was talking about keeping the database in memory
with fsync=off. Now I see he was only talking about the OS disk cache.
My server has 24GB RAM, and I cannot easily expand it unless I throw out
some 2GB modules, and buy more 4GB or 8GB modules. But... buying 4x8GB
ECC RAM (+throwing out 4x2GB RAM) is a lot more expensive than buying
some 64GB SSD drives. 95% of the table in question is not modified. Only
read (mostly with index scan). Only 5% is actively updated.
This is why I think, using SSD in my case would be effective.
Sorry for the confusion.
L
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