Re: SSD performance - Mailing list pgsql-performance

On Fri, 23 Jan 2009, Luke Lonergan wrote:

> Why not simply plug your server into a UPS and get 10-20x the
> performance using the same approach (with OS IO cache)?
>
> In fact, with the server it's more robust, as you don't have to transit
> several intervening physical devices to get to the RAM.
>
> If you want a file interface, declare a RAMDISK.
>
> Cheaper/faster/improved reliability.

you can also disable fsync to not wait for your disks if you trust your
system to never go down. personally I don't trust any system to not go
down.

if you have a system crash or reboot your RAMDISK will loose it's content,
this device won't.

also you are limited to how many DIMMS you can put on your motherboard
(for the dual-socket systems I am buying nowdays, I'm limited to 32G of
ram) going to a different motherboard that can support additional ram can
be quite expensive.

this isn't for everyone, but for people who need the performance, data
reliability, this looks like a very interesting option.

David Lang

> - Luke
>
> ----- Original Message -----
> From: pgsql-performance-owner@postgresql.org <pgsql-performance-owner@postgresql.org>
> To: Glyn Astill <glynastill@yahoo.co.uk>
> Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
> Sent: Fri Jan 23 04:39:07 2009
> Subject: Re: [PERFORM] SSD performance
>
> On Fri, 23 Jan 2009, Glyn Astill wrote:
>
>>> I spotted a new interesting SSD review. it's a $379
>>> 5.25" drive bay device that holds up to 8 DDR2 DIMMS
>>> (up to 8G per DIMM) and appears to the system as a SATA
>>> drive (or a pair of SATA drives that you can RAID-0 to get
>>> past the 300MB/s SATA bottleneck)
>>>
>>
>> Sounds very similar to the Gigabyte iRam drives of a few years ago
>>
>> http://en.wikipedia.org/wiki/I-RAM
>
> similar concept, but there are some significant differences
>
> the iRam was limited to 4G, used DDR ram, and used a PCI slot for power
> (which can be in
> short supply nowdays)
>
> this new drive can go to 64G, uses DDR2 ram (cheaper than DDR nowdays),
> gets powered like a normal SATA drive, can use two SATA channels (to be
> able to get past the throughput limits of a single SATA interface), and
> has a CF card slot to backup the data to if the system powers down.
>
> plus the performance appears to be significantly better (even without
> using the second SATA interface)
>
> David Lang
>
>
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