SAS vs. Fibre
One thing I hear about constantly (within the hallowed halls of EMC and elsewhere), is the general “inferiority” of SAS drives vs. Fibre. This usually comes complete with a somewhat stale argument that because SAS is a natural extension of SATA, it is therefore a “consumer” drive and not “good enough” for the Commercial or Enterprise disk space.
What most people fail to realize is the following:
a.) The platters, drive motors, heads, etc. are the same. If people actually spent the time looking into these products (vs. cutting at them with a wide swath of generalized foolishness), they’d actually see that the same mechanical “bits” make up both the “enterprise” class fibre and SAS drives. Looking at the Seagate Cheetah 15k.5 drive line, we see that they’re offered in SCA-40 (Fibre), SAS, SCA-80 (u320), and 68pin interfaces. The spec sheet shows that outside of differing transfer rates (and, lower power draws at load/idle than Fibre), both the SCSI and SAS drives are the same.
b.) The primary differentiators are the PCBs, ASICS, Physical Connectors to the “host” system, and Transfer Rates. Flipping the drives over, you’ll obviously note the differences in PCBs, onboard ASICs, and physical connectors. That’s a wash as it has little to nothing to do with reliability. So, what you’re left with is the transfer rate conundrum. Honestly, given how particularly bad customers are at actually filling a 4 gigabit per second pipe with data (esp. in the commercial side of the house), a 1 gigabit per second difference (roughly 100mb/s) is minimal. Oh, for the record, our STEC SSDs will only have a 2gb/s connection to the Symmetrix, last I heard. 😉
I think those two points about cover it. 😉 MTBF, etc. are the exact same, btw, so, don’t expect any differences from hardware longevity.
Engadget is one of my favourite reads during the day and consequently, I need to blog about articles located there more often. That being said, I almost fell out of my seat this morning when I read one of the latest postings: “Seagate warns it might sue SSD makers for patent infringement.” Yippee. In my opinion, this is more of the same “sue happy” nitwitery (is that a word?) that happens every single time Apple decides to release a new “product.” Some Rip van Winkle patent hound comes out of years of slumber and states “I patented the EXACT same technology using specious language and vague intimations of what I thought could work” much to the chagrin of everyone around. Now, in the case of Seagate and Western Digital, I believe that they’re just looking to diversify their holdings in the emerging SSD market. Remember, at the price per gigabyte/terabyte mark, spinning disk is still the king and will be for quite some time. However, in terms of power draw and raw IOPs, you can’t beat them. In any case, file this whole article under the “we want in (and the money wouldn’t be a bad thing either)” category. 😉
EDIT: (4/10/08 @ 1103pm EST) New entry added above on the Seagate vs. STEC lawsuit
Next on the hitlist is the re-emergence of Optical interconnects between processors as noted by Sun (and it’s recent DARPA grant). Great news for Sun, really, but IBM has already been doing this for some time. Optical interconnects ARE the wave of the future for processor interconnects, etc. especially as quantum computing (and it’s massive data loads) are concerned. Definitely something to pay attention to. Who knows? Maybe EMC will use optical transmission in its Symmetrix line between the blades. 😉 A boy can hope.
That’s all for now.