>> I know what you are saying, but I , wonder if it would be noticeable? I > > Well, "noticeable" again comes back to your workflow. As you point out > to Richard, it's (theoretically) 2x IOPS difference, which can be very > significant for some people. Yeah, but my point is if it would be noticeable to *me* (yes, I am a bit self-centered)
> I would say no, not even close to pushing it. Remember, we're > measuring performance in MBytes/s, and video throughput is measured in > Mbit/s (and even then, I imagine that a 27 Mbit/s stream over the air > is going to be pretty rare). So I'm figuring you're just scratching > the surface of even a minimal array. > > Put it this way: can a single, modern hard drive keep up with an > ADSL2+ (24 Mbit/s) connection? > Throw 24 spindles at the problem, and I'd say you have headroom for a > *lot* of streams. Sweet! I should probably hang-up this thread now, but there are too many other juicy bits to respond too... > I wasn't sure, with your workload. I know with mine, I'm seeing the > data store as being mostly temporary. With that much data streaming in > and out, are you planning on archiving *everything*? Cos that's "only" > one month's worth of HD video. Well, not to down-play the importance of my TV recordings, which is really a laugh because I'm not really a big TV watcher, I simply don't want to ever have to think about this again after getting it setup > I'd consider tuning a portion of the array for high throughput, and > another for high redundancy as an archive for whatever you don't want > to lose. Whether that's by setting copies=2, or by having a mirrored > zpool (smart for an archive, because you'll be less sensitive to the > write performance that suffers there), it's up to you... > ZFS gives us a *lot* of choices. (But then you knew that, and it's > what brought you to the list :) All true, but if 4(4+2) serves all my needs, I think that its simpler to administrate as I can arbitrarily allocate space as needed without needing to worry about what kind of space it is - all the space is "good and fast" space... > I also committed to having at least one hot spare, which, after > staring at relling's graphs for days on end, seems to be the cheapest, > easiest way of upping the MTTDL for any array. I'd recommend it. No doubt that a hot-spare gives you a bump in MTTDL, but double-parity trumps it big time - check out Richard's blog... > As I understand it, 5(2+1) would scale to better IOPS performance than > 4(4+2), and IOPS represents the performance baseline; as you ask the > array to do more and more at once, it'll look more like random seeks. > > What you get from those bigger zvol groups of 4+2 is higher > performance per zvol. That said, with my few datapoints on 4+1 RAID-Z > groups (running on 2 controllers) suggest that that configuration runs > into a bottleneck somewhere, and underperforms from what's expected. Er? Can anyone fill in the missing blank here? > Oh, the bus will far exceed your needs, I think. > The exercise is to specify something that handles what you need > without breaking the bank, no? Bank, smank - I build a system every 5+ years and I want it to kick ass all the way until I build the next one - cheers! > BTW, where are these HDTV streams coming from/going to? Ethernet? A > capture card? (and which ones will work with Solaris?) Glad you asked, for the lists sake, I'm using two HDHomeRun tuners (http://www.silicondust.com/wiki/products/hdhomerun) - actually, I bought 3 of them because I felt like I needed a spare :-D > Yeah, perhaps I've been a bit too circumspect about it, but I haven't > been all that impressed with my PCI-X bus configuration. Knowing what > I know now, I might've spec'd something different. Of all the > suggestions that've gone out on the list, I was most impressed with > Tim Cook's: > >> Won't come cheap, but this mobo comes with 6x pci-x slots... should >> get the job done :) >> >> http://www.supermicro.com/products/motherboard/Xeon1333/5000P/X7DBE-X.cfm >> > > That has 3x 133MHz PCI-X slots each connected to the Southbridge via a > different PCIe bus, which sounds worthy of being the core of the > demi-Thumper you propose. Yeah, but getting back to PCIe I see these tasty SAS/SATA HBAs from LSI: http://www.lsi.com/storage_home/products_home/host_bus_adapters/sas_hbas/lsisas3081er/index.html (note, LSI also sells matching PCI-X HBA controllers, in case you need to balance your mobo's architecture] > ...But.... It all depends what you intend to spend. (This is what I > was going to say in my next blog entry on the system:) We're talking > about benchmarks that are really far past what you say is your most > taxing work load. I say I'm "disappointed" with the contention on my > bus putting limits on maximum throughputs, but really, what I have far > outstrips my ability to get data into or out of the system. So moving to the PCIe-based cards should fix that - no? > So all of my "disappointment" is in theory. Seems like this should be a classic quote, but a google-search on "disappointment is in theory" only turns up this list - seriously, only one result... Best, Kent _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
