Tracy Reed <[email protected]> writes: > On Sun, Sep 06, 2009 at 10:56:16AM -0400, Edward Ned Harvey spake thusly: > I have done such tests but I don't have them at hand to share with you > at the moment. Expensive single disks such as 15k SAS can do > 1Gb/s. But your typical 7.2k RPM SATA does 50-70 it seems. I will see > if I can dig some up. The nice thing about AoE is that there is little > to no network overhead. It is not TCP nor IP. It runs purely at layer > 2.
My experience has been I can expect something between 70-100megabytes/sec for 7500RPM, depending on where in the disk it is. if I get 50MB/sec on the outer tracks, I assume the drive has a bunch of remapped sectors and I send it back. (this is for 1.5TiB or 1TiB drives with 32MiB cache.) I only expect 120Megabytes/sec out of a 15K drive; The big win with 15K drives is not sequential speed (the higher density of the sata drives help with that) but random access speed. Anyhow, with my workload, I never have sequential access. I've got a bunch of virtuals sharing a disk, so all access, even if it looked sequential from within the DomU, is random. So yeah; a few bonded gigabit links seems reasonable to me for as many drives as I can fit in one chassis. > > PS. 2G of ram in a server doesn't sound like much to me. I never buy any > > laptop with less than 4G anymore. > > The 2G I was refering to is in the SAN head. Not the server running > the virual machines. The 2G in each SAN head is there just to run the > kernel, vblade, and provide caching. RAM is so cheap that future > machines may have 4 or 8G depending on how this affects the > price/performance. RAM is so cheap now that I expect we will just go > 8G. Yeah, I always fill a motherboard to the max. it economically supports; 8GiB, usually, for single-sockets, 32 or 64GiB for dual-socket boards. For a highly random load like mine, ram cache makes a big difference, much bigger, I think, than the difference between 2G and 4g links. _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
