Hi At least with SSD's the MLC's outnumber the SLC's by a very wide margin. Where I shop it's at least 30:1 in favor of the MLC's. That can put you into a "Joe No Name SLC" vs a brand name MLC decision.
Next up is price. I'm seeing a 3 to 5X premium for the SLC's. That's a big jump, and it's not getting any smaller with time. The question becomes - will a 2X larger name brand MLC outlast a SLC *if* you never write to the second half of the disk? With any of them, you need to be sure that the batch you bought has "good" controllers in it. I can demonstrate controller issues pretty fast. I know - lots of questions - not a lot of answers .... Right now I'm on the 2X larger approach. We'll see how it goes. Bob On Feb 2, 2010, at 4:45 AM, Bernd Walter wrote: > On Sun, Jan 31, 2010 at 01:59:47PM -0700, David Alexander wrote: >> On Sat, 30 Jan 2010 08:50:09 +0000, "Poul-Henning Kamp" >> <p...@phk.freebsd.dk> wrote: >> >>> In message <3f8f34c5-f376-46b0-9e2c-53a213d0e...@cq.nu>, Bob Camp writes: >>> >>>>> Don't get an SSD thinking you're going to get speed. The 5501 will >>>>> limit the throughput well below what you'd expect for an SSD. >>> >>> An SSD still does miracles for access time. >> >> Yes it does. I should have mentioned that the one thing that drove me >> to buy the SSD was how poorly my CF card handled multiple simultaneous >> requests. For example, when I open my email client it syncs all the >> folders with the IMAP server in parallel. This was painfully slow on >> the CF card which is designed to read or write a single file at a >> time. Switching to the SSD made a significant improvement in parallel >> operations. > > As a rule of thumb: buy media based on SLC and not MLC flash. > Technically it is something different and I have been seen MLC cards > without this problem, but I've also seen that productions silently > changed and the next bunch of the same card is slow. > Many cheap cards today have the problem that they just care to be fast > when writing linear in large chunks, which is Ok for cameras using > msdosfs to write large pictures. > I think the real reson behind is a simplified wear leveling technik. > I've seen MLC cards degrading down to less than 10 transactions per > second, which is really painfull if the OS decides to flush buffers. > > Another rule of thumb is that flash blocks are in the 4k or 8k range. > If you write smaller chunks the card is doing read modify write cycles. > Moreover I noticed that it is horribly slow to write to the same > physical block again, so writing continuous 8k in two 4k chunks is a > very bad strategy. > This is also true for SLC cards, but they don't undergo that heavy speed > penalty as some MLC cards do. > Use a big and properly aligned filesystem blocksize and you should see > much better results. > > -- > B.Walter <be...@bwct.de> http://www.bwct.de > Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm. > _______________________________________________ > Soekris-tech mailing list > Soekris-tech@lists.soekris.com > http://lists.soekris.com/mailman/listinfo/soekris-tech > _______________________________________________ Soekris-tech mailing list Soekris-tech@lists.soekris.com http://lists.soekris.com/mailman/listinfo/soekris-tech
