So can anybody help answering these questions: - are there any special options when creating the RAID0 to make it perform faster for such a use case? - are there other tunables, any special MD / LVM / file system / read ahead / buffer cache / ... parameters to look for? lets see: what´s your disk (ssd or sas or sata) best block size to write/read? write this at ->(A) what´s your work load? 50% write 50% read ? raid0 block size should be multiple of (A) *****filesystem size should be multiple of (A) of all disks *****read ahead should be a multiple of (A) for example /dev/sda 1kb /dev/sdb 4kb you should use 6kb... you should use 4kb, 8kb, 16kb (multiple of 1kb and 4kb) check i/o sheduller per disk too (ssd should use noop, disks should use cfq, deadline or another...) async and sync option at mount /etc/fstab, noatime reduce a lot of i/o too, you should optimize your application too hdparm each disk to use dma and fastest i/o options are you using only filesystem? are you using somethink more? samba? mysql? apache? lvm? each of this programs have some tunning, check their benchmarks getting back.... what´s a raid controller? cpu + memory + disk controller + disks but... it only run raid software (it can run linux....) if you computer is slower than raid cpu+memory+disk controller, you will have a slower software raid, than hardware raid it´s like load balance on cpu/memory utilization of disk i/o (use dedicated hardware, or use your hardware?) got it? using a super fast xeon with ddr3 and optical fiber running software raid, is faster than a hardware raid using a arm (or fpga) ddrX memory and sas(fiber optical) connection to disks two solutions for the same problem what´s fast? benchmark it i think that if your xeon run a database and a very workloaded apache, a dedicated hardware raid can run faster, but a light xeon can run faster than a dedicated hardware raid 2011/1/19 Wolfgang Denk <wd@xxxxxxx>: > Dear =?ISO-8859-15?Q?Stefan_/*St0fF*/_H=FCbner?=, > > In message <4D361F26.3060507@xxxxxxxxxxxxxxxxxx> you wrote: >> >> [in German:] Schätzelein, Dein Problem sind die Platten, nicht der >> Controller. >> >> [in English:] Dude, the disks are your bottleneck. > ... > > Maybe we can stop speculations about what might be the cause of the > problems in some setup I do NOT intend to use, and rather discuss the > questions I asked. > >> > 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. > > Clarrification: I'll run /dev/md* on the raw disks, without any > partitions on them. > >> > My goal is to optimize for maximum number of I/O operations per >> > second. ... >> > >> > 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?] > > So can anybody help answering these questions: > > - are there any special options when creating the RAID0 to make it > perform faster for such a use case? > - are there other tunables, any special MD / LVM / file system / > read ahead / buffer cache / ... parameters to look for? > > Thanks. > > Wolfgang Denk > > -- > DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany > Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@xxxxxxx > Boykottiert Microsoft - Kauft Eure Fenster bei OBI! > -- > 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
