My P4-2.4GHz with 3 WD80G 8MB caches does significantly better with RAID5
hdparm -tT /dev/md/3
/dev/md/3:
Timing buffer-cache reads: 1844 MB in 2.00 seconds = 921.08 MB/sec
Timing buffered disk reads: 166 MB in 3.00 seconds = 55.26 MB/sec
md3 : active raid5 ide/host4/bus0/target0/lun0/part3[1]
ide/host2/bus1/target0/lun0/part3[2]
ide/host2/bus0/target0/lun0/part3[0]
143713280 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
Linux why 2.4.22-ck2-blackbox-aph-21 #1 Wed Sep 17 09:41:14 EDT 2003 i686
GNU/Linux
This kernel also has the low latency and preempt patches applied and running
at 500hz.
Andrew
----- Original Message -----
From: "Hermann Himmelbauer" <dusty@strike.wu-wien.ac.at>
To: "Gordon Henderson" <gordon@drogon.net>; <linux-raid@vger.kernel.org>
Sent: Monday, October 27, 2003 6:01 AM
Subject: Re: RAID1 VS RAID5
> On Monday 27 October 2003 10:19, Gordon Henderson wrote:
> > On Mon, 27 Oct 2003, Hermann Himmelbauer wrote:
> > > My experience is that software RAID5 is quite slow.
> >
> > My experiences are the opposite to yours I'm afraid - I've not found it
> > any slower than a single drive and in some cases a lot faster!
> >
> > A lot depends on exactly what you are doing with it though, but I'm
> > willing to sacrifice some speed for data integrity.
> >
> > Most of my systems are network servers with 100Mb Network cards fitted -
> > as long as my disk systems are faster than 12.5MB/sec I'm happy. In
> > practice I can stream 50MB/sec+ out of some simple RAID5 IDE systems I
> > have.
>
> Well - I have an old Dual P-II-266 System with an onboard SCSI-Controller
with
> 3 Ultra SCSI-disks connected, building a RAID5. I did a simple Test with
> "hdparm -tT" to provide you with numbers:
>
> /dev/sdb:
> Timing buffer-cache reads: 128 MB in 1.46 seconds = 87.67 MB/sec
> Timing buffered disk reads: 64 MB in 5.07 seconds = 12.62 MB/sec
>
> /dev/sdc:
> Timing buffer-cache reads: 128 MB in 1.47 seconds = 87.07 MB/sec
> Timing buffered disk reads: 64 MB in 4.78 seconds = 13.39 MB/sec
>
> /dev/sdd:
> Timing buffer-cache reads: 128 MB in 1.49 seconds = 85.91 MB/sec
> Timing buffered disk reads: 64 MB in 5.05 seconds = 12.67 MB/sec
>
> So you see, the seperate disks achieve ~ 13MB/s. My RAID5 raidtab looks
like
> this:
> raiddev /dev/md0
> raid-level 5
> nr-raid-disks 3
> nr-spare-disks 0
> chunk-size 4
> persistent-superblock 1
> parity-algorithm left-symmetric
> device /dev/sdb2
> raid-disk 0
> device /dev/sdc2
> raid-disk 1
> device /dev/sdd2
> raid-disk 2
>
> And "hdparm -tT" looks like this:
>
> /dev/md0:
> Timing buffer-cache reads: 128 MB in 1.45 seconds = 88.28 MB/sec
> Timing buffered disk reads: 64 MB in 13.85 seconds = 4.62 MB/sec
>
> So this is ~ 1/3rd of the read performance of a single disk. And this is
what
> a appr. measure when copying files etc.
>
> My kernel version is 2.4.20 and the CPU-Load during the hdparm test is
only at
> ~ 30%.
>
> Best Regards,
> Hermann
>
> --
> x1@aon.at
> GPG key ID: 299893C7 (on keyservers)
> FP: 0124 2584 8809 EF2A DBF9 4902 64B4 D16B 2998 93C7
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> 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@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
