Also seems pretty silly to put it on a regular SATA connection, when all that can manage is 150MB/sec. If you made it connection directly to 66/64-bit PCI then it could actualy _use_ the speed of the RAM, not to mention PCI-X.
Alex Turner NetEconomist On 7/26/05, John A Meinel <[EMAIL PROTECTED]> wrote: > I saw a review of a relatively inexpensive RAM disk over at > anandtech.com, the Gigabyte i-RAM > http://www.anandtech.com/storage/showdoc.aspx?i=2480 > > Basically, it is a PCI card, which takes standard DDR RAM, and has a > SATA port on it, so that to the system, it looks like a normal SATA drive. > > The card costs about $100-150, and you fill it with your own ram, so for > a 4GB (max size) disk, it costs around $500. Looking for solid state > storage devices, the cheapest I found was around $5k for 2GB. > > Gigabyte claims that the battery backup can last up to 16h, which seems > decent, if not really long (the $5k solution has a built-in harddrive so > that if the power goes out, it uses the battery power to copy the > ramdisk onto the harddrive for more permanent storage). > > Anyway, would something like this be reasonable as a drive for storing > pg_xlog? With 4GB you could have as many as 256 checkpoint segments. > > I'm a little leary as it is definitely a version 1.0 product (it is > still using an FPGA as the controller, so they were obviously pushing to > get the card into production). > > But it seems like this might be a decent way to improve insert > performance, without setting fsync=false. > > Probably it should see some serious testing (as in power spikes/pulled > plugs, etc). I know the article made some claim that if you actually > pull out the card it goes into "high consumption mode" which is somehow > greater than if you leave it in the slot with the power off. Which to me > seems like a lot of bull, and really means the 16h is only under > best-case circumstances. But even 1-2h is sufficient to handle a simple > power outage. > > And if you had a UPS with detection of power failure, you could always > sync the ramdisk to a local partition before the power goes out. Though > you could do that with a normal in-memory ramdisk (tmpfs) without having > to buy the card. Though it does give you up-to an extra 4GB of ram, for > machines which have already maxed out their slots. > > Anyway, I thought I would mention it to the list, to see if anyone else > has heard of it, or has any thoughts on the matter. I'm sure there are > some people who are using more expensive ram disks, maybe they have some > ideas about what this device is missing. (other than costing about > 1/10th the price) > > John > =:-> > > > > ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend