4 ms·
Hmmm yes, you're right. Even with knowledge of the accesses required in 1s time, you're still bounded by the speed of the movements of the heads. That said. I
by sadiq 17y ago
Hmmm yes, you're right.
Even with knowledge of the accesses required in 1s time, you're still bounded by the speed of the movements of the heads.
That said. I wonder if there's any trickery you can do with pre-generating the interleaved data for a group of users.
As in:
1) Read the next 5 (or any amount really) tracks for each of the users in a group.
2) Interleave the 16KB blocks in the same pattern you'd be streaming.
Step 1 is just a whole set of sequential reads. Step 2 is one big sequential write. Then your streaming operation is a single sequential read.
Of course, there's a good chance the overhead on doing the above outweighs the gain.
- russss 17y agoBut you've got the additional bonus problem that users can skip Last.fm tracks at any time, so there's a pretty high probability that you won't need all that data anyway. (I used to work for Last.fm and we spent a fair amount of time working on this issue without a great amount of success.)
- sadiq 17y agoD'oh, I hadn't considered that. I'm also wondering what moved them towards the SLC-based Intel drives as opposed to the MLC-based ones (that offer a much lower price-capacity), since in terms of read performance IOPS they're almost identical.
- kogir 17y agoProbably reliability. From Intel's docs: X25-M: 1,200,000 Hours X25-E: 2,000,000 Hours I'd be willing to replace them more regularly for the added capacity though.
- chrisbolt 17y agoX25-M 80GB: $270 X25-E 64GB: $890 At that price you can buy 3 X25-Ms and still have more space. The real difference is in write cycles though: the X25-E can do ten times as many as the X25-M.
- lozzd2 17y agoWe were going to go for the larger sized (space wise) MLC based ones except that they're in the smaller form factor, not easy to fit in the server chassis. The connector on them is also non standard, unlike the MLC models which slide right in. Makes a big difference when you're buying a lot of them. Also, if we ever decide to re-commission these machines later, the SLC based ones will be more useful for us.
- chrisbolt 17y agoI've been using both the MLC and SLC Intels and they both have the same standard SATA connector. Also, server chassis are moving to 2.5" SATA bays, our latest servers have 2 dual processor motherboards in 1U (Supermicro calls them 1U-twin), with 4 2.5" bays for each motherboard.
- lozzd 17y agoThe chassis has 2.5" bays, and so do the SSDs we used. However, the only MLC SSDs available were 1.8" versions, hence my comment. We had to work pretty hard to get any of them!