On Mon, May 12, 2008 at 8:04 PM, Francisco Reyes <lists@xxxxxxxxxxxxxxxx> wrote: > Inheritted a number of servers and I am starting to look into the hardware. > > So far what I know from a few of the servers > Redhat servers. > 15K rpm disks, 12GB to 32GB of RAM. > Adaptec 2120 SCSI controller (64MB of cache). Considering the generally poor performance of adaptec RAID controllers, you'd probably be better off with 12 SATA drives hooked up to an escalade or Areca card (or cards). Since you seem to want a lot of storage, a large array of SATA disks may be a better balance between performance and economy. > The servers have mostly have 12 drives in RAID 10. > We are going to redo one machine to compare RAID 10 vs RAID 50. Mostly to > see if the perfomance is close, the space gain may be usefull. See the remark about SATA drives above. With 12 750Gig drives, you'd have 6*750G of storage in RAID-10, or about 4.5 Terabytes of redundant storage. > The usage pattern is mostly large set of transactions ie bulk loads of > millions of rows, queries involving tens of millions of rows. > A few questions. > Will it pay to go to a controller with higher memory for existing machines? Then no matter how big your cache on your controller, it's likely NOT big enough to ever hope to just swallow the whole set at once. Bigger might be better for a lot of things, but for loading, a good controller is more important. An increase from 64M to 256M is not that big in comparison to how big your datasets are likely to be. > The one machine I am about to redo has PCI which seems to somewhat limit our > options. You do know that you can plug a PCI-X card into a PCI slot, right? (see the second paragraph here: http://en.wikipedia.org/wiki/PCI-X#Technical_description) So, you can get a nice card today, and if needs be, a better server to toss it in tomorrow. Where I work we have a nice big machine in production with a very nice PCI-X card (Not sure which one, my cohort ordered it) and we wanted out in house testing machine to have the same card, but that machine is much less powerful. Same card fit, so we can get some idea about I/O patterns on the test box before beating on production. > A few questions. > Will it pay to go to a controller with higher memory for existing machines? Pay more attention to the performance metrics the card gets from people testing it here. Areca, Escalade / 3Ware, and LSI get good reviews, with LSI being solid but a little slower than the other two for most stuff. > For large setups (ie 500GB+ per server) does it make sense to try to get a > controller in a machine or do SANs have better throughput even if at a much > higher cost? SANs generally don't have much better performance, and cost MUCH more per meg stored. They do however have some nice management options. If a large number of disks in discrete machines presents a problem of maintenance, the SAN might help, but given the higher cost, it's often just cheaper to keep a box of disks handy and have a hardware person replace them. > For future machines I plan to look into controllers with at least 512MB, > which likely will be PCI-X/PCI-e.. not seen anything with large caches for > PCI. See remark about PCI-X / PCI > Also the machines in question have SCSI drives, not SAS. I believe the > most recent machine has SAS, but the others may be 15K rpm scsi > Whether a SAN or just an external enclosure is 12disk enough to substain 5K > inserts/updates per second on rows in the 30 to 90bytes territory? You'll only know by testing, and a better RAID controller can make a WORLD of difference here. Just make sure whatever controller you get has battery backed cache, and preferably a fair bit of it. Some controllers can handle 1G+ of memory.
