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@xxxxxxxxxxxxxx <pgsql-performance-owner@xxxxxxxxxxxxxx>
To: Glyn Astill <glynastill@xxxxxxxxxxx>
Cc: pgsql-performance@xxxxxxxxxxxxxx <pgsql-performance@xxxxxxxxxxxxxx>
Sent: Fri Jan 23 04:39:07 2009
Subject: Re: 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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