On Wed, Jan 19, 2011 at 09:18:22PM -0200, Roberto Spadim wrote: > a good idea.... > why not start a opensource raid controller? > what we need? a cpu, memory, power supply with battery or capacitor, > sas/sata (disk interfaces), pci-express or another (computer > interface) Why? because of some differences in memory speed? Normally software raid is faster than hardware raid, as wittnessed by many here on the list. The mentioning of max 350 MB/s on a SW raid is not true, 350 MB/S is what I get out of a simple box with 4 slightly oldish SATA drives. 16 new fast SATA drives in SW raid6 should easily go beyond 1000 MB/s, given that there are not other bottlenecks in the system. Linux SW raid goes fairly close to theoretical maxima, given adequate HW. best regards keld > it don?t need a operational system, since it will only run one program > with some threads (ok a small operational system to implement threads > easly) > > we could use arm, fpga, intel core2duo, atlhon, xeon, or another system... > instead using a computer with ethernet interface (nbd nfs samba or > another file/device sharing iscsi ethernet sata), we need a computer > with pci-express interface and native operational system module > > > 2011/1/19 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > > the problem.... > > if you use iostat, or iotop > > with software raid: > > you just see disk i/o > > you don?t see memory (cache) i/o > > when using hardware raid: > > you just see raid i/o (it can be a cache read or a real disk read) > > > > > > if you check memory+disk i/o, you will get similar values, if not, you > > will see high cpu usage > > for example you are using raidx with 10disks on a hardware raid > > change hardware raid to use only disks (10 disks for linux) > > make the same raidx with 10disks > > you will get a slower i/o since it have a controler between disk and cpu > > try it without hardware raid cpu, just a (sas/sata) optimized > > controller, or 10 (sata/sas) one port > > you still with a slow i/o then hardware controller (that?s right!) > > > > now let?s remove the sata/sas channel, let?s use a pci-express > > revodrive or pci-express texas ssd drive > > you will get better values then a hardware raid, but... why? you > > changed the hardware (ok, i know) but you make cpu more close to disk > > if you use disks with cache, you will get more speed (a memory ssd > > harddisk is faster than a harddisk only disk) > > > > why hardware are more faster than linux? i don?t think they are... > > they can make smaller latencies with good memory cache > > but if you computer use ddr3 and your hardware raid controller use i2c > > memory, your ddr3 cache is faster... > > > > how to benchmark? check disk i/o+memory cache i/o > > if linux is faster ok, you use more cpu and memory of your computer > > if linux is slower ok, you use less cpu and memory, but will have it > > on hardware raid... > > if you upgrade you memory and cpu, it can be faster than you hardware > > raid controller, what?s better for you? > > > > want a better read/write solution for software raid? make a new > > read/write code, you can do it, linux is easier than hardware raid to > > code! > > want a better read/write solution for hardware raid? call your > > hardware seller and talk, please i need a better firmware, could you > > send me? > > > > got? > > > > > > 2011/1/19 Stefan /*St0fF*/ Hübner <stefan.huebner@xxxxxxxxxxxxxxxxxx>: > >> @Roberto: I guess you're right. BUT: i have not seen 900MB/s coming from > >> (i.e. read access) a software raid, but I've seen it from a 9750 on a > >> LSI SASx28 backplane, running RAID6 over 16disks (HDS722020ALA330). So > >> one might not be wrong assuming on current raid-controllers > >> hardware/software matching and timing is way more optimized than what > >> mdraid might get at all. > >> > >> The 9650 and 9690 are considerably slower, but I've seen 550MB/s thruput > >> from those, also (I don't recall the setup anymore, tho). > >> > >> Max reading I saw from a software raid was around 350MB/s - so hence my > >> answers. And if people had problems with controllers which are 5 years > >> or older by now, the numbers are not really comparable... > >> > >> Now again there's the point where there are also parameters on the > >> controller that can be tweaked, and a simple way to recreate the testing > >> scenario. We may discuss and throw in further numbers and experience, > >> but not being able to recreate your specific scenario makes us talk past > >> each other... > >> > >> stefan > >> > >> Am 19.01.2011 20:50, schrieb Roberto Spadim: > >>> 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 > >>>> > >>> > >>> > >>> > >> > >> -- > >> 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 > > > > > > -- > 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 -- 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
