I've also looked at the Fusion-IO products. They are not standard flash drives. They don't appear as SATA devices. They contains an FPGA that maps the flash directly to the PCI bus. The kernel-mode drivers blits data to/from them via DMA, not a SATA or SAS drive (that would limit transfer rates to 6Gb/s). But, I don't have any in-hand to test with yet... :( But the kool-aide looks tasty :) On Thu, Mar 8, 2012 at 8:52 AM, Merlin Moncure <mmoncure@xxxxxxxxx> wrote: > On Wed, Mar 7, 2012 at 2:54 AM, Joel Jacobson <joel@xxxxxxxxxxx> wrote: >> My company is in the process of migrating to a new pair of servers, running 9.1. >> >> The database performance monetary transactions, we require >> synchronous_commit on for all transactions. >> >> Fusion-io is being considered, but will it give any significant >> performance gain compared to normal SATA-based SSD-disks, due to the >> fact we must replicate synchronously? >> >> To make it more complicated, what about SLC vs MLC (for synchronous >> replication)? >> >> Assume optimal conditions, both servers have less than a meter between >> each other, with the best possible network link between them providing >> the lowest latency possible, maxed out RAM, maxed out CPUs, etc. >> >> I've already asked this question to one of the core members, but the >> answer was basically "you will have to test", I was therefore hoping >> someone in the community already had some test results to avoid >> wasting money. >> >> Thank you for any advice! > > flash, just like hard drives, has some odd physical characteristics > that impose some performance constraints, especially when writing, and > double especially when MLC flash is used. modern flash drives employ > non volatile buffers to work around these constraints that work pretty > well *most* of the time. since MLC is much cheaper improvements in > flash controller technology are basically pushing SLC out of the > market except in high end applications. > > if you need zero latency storage all the time and are willing to spend > the extra bucks, then pci-e based SLC is definitely worth looking at > (you'll have another product to evaluate soon when the intel 720 > ramsdale hits the market). a decent MLC drive might work for you > though, i'd suggest testing there first and upgrading to the expensive > proprietary stuff if and only if you really need it. > > my experience with flash and postgres is that even with low-mid range > drives like the intel 320 it's quite a challenge to make postgres be > i/o bound. > > merlin > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
