maybe removing hwraid and using swraid may reduce speed (depend how much cpu you use with hw and with sw) what we can optimize? less I/O per seconds making as much useful read/write data on array, how? good read/write algorithms for raid. (for each device type, ssd, hd) but... like stefan, disks are your bottleneck 2011/1/18 Stefan /*St0fF*/ Hübner <stefan.huebner@xxxxxxxxxxxxxxxxxx>: > Hi, > > [in German:] Schätzelein, Dein Problem sind die Platten, nicht der > Controller. > > [in English:] Dude, the disks are your bottleneck. > > On a 4-disk RAID0 software RAID can only outspeed this 3ware Controller > with a really really fast processor. The limiting factor is the disk's > access time. If SSDs are too expensive, then your actual performance is > the max you'll get (maybe to replace the HWRAID controller might give a > little speed-up, but not very much). > > All the best, > Stefan > > Am 18.01.2011 22:01, schrieb Wolfgang Denk: >> Hi, >> >> I'm going to replace a h/w based RAID system (3ware 9650SE) by a plain >> s/w RAID0, because the existing system appears to be seriously limited >> in terms of numbers of I/O operations per second. >> >> Our workload is mixed read / write (something between 80% read / 20% >> write and 50% / 50%), consisting of a very large number of usually >> very small files. >> >> There may be 20...50 millions of files, or more. 65% of the files are >> smaller than 4 kB; 80% are smaller than 8 kB; 90% are smaller than 16 >> kB; 98.4% are smaller than 64 kB. >> >> I will have 4 x 1 TB disks for this setup. >> >> The plan is to build a RAID0 from the 4 devices, create a physical >> volume and a volume group on the resulting /dev/md?, then create 2 or >> 3 logical volumes that will be used as XFS file systems. >> >> My goal is to optimize for maximum number of I/O operations per >> second. [I am aware that using SSDs would be a nice thing, but that >> would be too expensive.] >> >> Is this a reasonable approach for such a task? >> >> Should I do anything different to acchive maximum performance? >> >> What are the tunables in this setup? [It seems the usual recipies are >> more oriented in maximizing the data troughput for large, mostly >> sequential accesses - I figure that things like increasing read-ahead >> etc. will not help me much here?] >> >> Thanks in advance. >> >> Best regards, >> >> Wolfgang Denk >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
