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) 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
