1. it is not good to use so many disks in one raid. this means that in
degraded mode
10 disks would be needed to reconstruct one slice of data.
2. i did not understand what is raid purpose.
3. 10 MB/s is very slow. what sort of disks do u have ?
4. what is the raid stripe size ?
On 1/4/06, JaniD++ <djani22@xxxxxxxxxxxxx> wrote:
>
> ----- Original Message -----
> From: "Raz Ben-Jehuda(caro)" <raziebe@xxxxxxxxx>
> To: "JaniD++" <djani22@xxxxxxxxxxxxx>
> Cc: "Linux RAID Mailing List" <linux-raid@xxxxxxxxxxxxxxx>
> Sent: Wednesday, January 04, 2006 2:49 PM
> Subject: Re: raid5 read performance
>
>
> > 1. do you want the code ?
>
> Yes.
> If it is difficult to set.
> I use 4 big raid5 array (4 disk node), and the performace is not too good.
> My standalone disk can do ~50MB/s, but 11 disk in one raid array does only
> ~150Mbit/s.
> (With linear read using dd)
> At this time i think this is my systems pci-bus bottleneck.
> But on normal use, and random seeks, i am happy, if one disk-node can do
> 10MB/s ! :-(
>
> Thats why i am guessing this...
>
> > 2. I managed to gain linear perfromance with raid5.
> > it seems that both raid 5 and raid 0 are caching read a head buffers.
> > raid 5 cached small amount of read a head while raid0 did not.
>
> Aham.
> But...
> I dont understand...
> You wrote that, the RAID5 is slower than RAID0.
> The read a head buffering/caching is bad for performance?
>
> Cheers,
> Janos
>
>
> >
> >
> > On 1/4/06, JaniD++ <djani22@xxxxxxxxxxxxx> wrote:
> > >
> > > ----- Original Message -----
> > > From: "Raz Ben-Jehuda(caro)" <raziebe@xxxxxxxxx>
> > > To: "Mark Hahn" <hahn@xxxxxxxxxxxxxxxxxxx>
> > > Cc: "Linux RAID Mailing List" <linux-raid@xxxxxxxxxxxxxxx>
> > > Sent: Wednesday, January 04, 2006 9:14 AM
> > > Subject: Re: raid5 read performance
> > >
> > >
> > > > I guess i was not clear enough.
> > > >
> > > > i am using raid5 over 3 maxtor disks. the chunk size is 1MB.
> > > > i mesured the io coming from one disk alone when I READ
> > > > from it with 1MB buffers , and i know that it is ~32MB/s.
> > > >
> > > > I created raid0 over two disks and my throughput grown to
> > > > 64 MB/s.
> > > >
> > > > Doing the same thing with raid5 ended in 32 MB/s.
> > > >
> > > > I am using async io since i do not want to wait for several disks
> > > > when i send an IO. By sending a buffer which is striped aligned
> > > > i am supposed to have one to one relation between a disk and an
> > > > io.
> > > >
> > > > iostat show that all of the three disks work but not fully.
> > >
> > > Hello,
> > >
> > > How do you set sync/async io?
> > > Please, let me know! :-)
> > >
> > > Thanks,
> > > Janos
> > >
> > >
> > >
> >
> >
> > --
> > Raz
>
>
--
Raz
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