Quote:
Originally Posted by Aevum /img/forum/go_quote.gif
remember to get MLC drives, not SLC,
SLC might be faster, buy MLC has less sector density, so it will have lower failiure rates,
|
Wrong! multi-level cells have 2 (soon 4) bits per cell for higher density but you pay the price in speed and reliability. single-level cells are rated at 100,000 write cycles, MLC only 10,000 or so.
The drives have fairly complex circuitry inside to remap failed cells (NAND flash has really weird failure modes), and headroom. According to an Intel rep I talked with last week, the X25-E has 64MB of internal flash, but 50% of that is reserved so it can provide 32MB of usable capacity for the expected 5 year lifetime of an enterprise drive. Like all MLC drives, the X25-M is a laptop HDD replacement drive and has lower redundancy and duty cycles.
Be careful about cheap SSD drives. Some controllers have poor implementation and are quite unreliable in extended use.
Intel is currently the leader in SATA SSDs - the X25-E can sustain 4,000 iops with a read
and write latency of 100
microseconds, 200MBps read and 170MBps write. There is no spinning rust drive out there that comes even close.
The absolute performance champ is FusionIO, though. Their drives post 600+ MBps because they sit directly on the PCIe bus and don't go through the bottleneck of SATA and drivers optimized for devices with rotational latency. The flip side is that they need drivers as they are not recognized as a standard device (they don't have Solaris drivers yet, for instance, although they are reportedly working on them).
I picked up a 32GB X25-E to benchmark databases on, and am looking forward to using it as the boot drive on my Nehalem Mac Pro when I receive it later this month. I don't know if Snow Leopard will include Sun's recent ZIL and L2ARC enhancements to ZFS. They allow you to get the speed benefits of SSD with the price per TB of HDD. For more details, check out the
OpenSolaris Storage Summit slides.
A tip: most SSDs come in 2.5" form factors. If you need an adapter for 3.5" slots, consider the
IcyDock adapter ($20 at NewEgg), as it is the only one that has the connectors in the right place for drive carriers like the one on Mac Pros.