[mythtv-users] Fastest RAID for HD?

Sun Feb 17 04:53:39 UTC 2008

Interesting that the read performance on system 2 seems to be 3 times that the write speed, whereas it’s only 2 times the speed on system 1. I wonder if it’s the faster processor, the additional memory or the fact that there is only 1 PATA drive (or a combination of all).

G

System1

CPU0: Intel(R) Pentium(R) 4 CPU 1.60GHz stepping 02

Memory: 382140k/393152k available

RAID 5 array of 9 x 320Gb disks 3 PATA, 6 SATA

[root at datastore00]# dd if=/dev/zero of=testfile bs=1M count=16384

16384+0 records in

16384+0 records out

17179869184 bytes (17 GB) copied, 412.86 seconds, 41.6 MB/s

[root at datastore00]# dd if=testfile of=/dev/null bs=1M

16384+0 records in

16384+0 records out

17179869184 bytes (17 GB) copied, 232.732 seconds, 73.8 MB/s

System2

CPU0: Intel(R) Pentium(R) 4 CPU 2.40GHz stepping 09

Memory: 1030808k/1048496k available

RAID 5 array of 5 x 500Gb disks 1 PATA, 4 SATA

[root at datastore01]# dd if=/dev/zero of=testfile bs=1M count=16384

16384+0 records in

16384+0 records out

17179869184 bytes (17 GB) copied, 283.396 s, 60.6 MB/s

[root at datastore01]# dd if=testfile of=/dev/null bs=1M

16384+0 records in

16384+0 records out

17179869184 bytes (17 GB) copied, 100.8 s, 170 MB/s

From: mythtv-users-bounces at mythtv.org [mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Gerald Brandt
Sent: Saturday, February 16, 2008 12:30 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Fastest RAID for HD?

my system is an AMD 64 X2 3800+ with 2 GB RAM.

I have 5 250 GB HDD in a software RAID5.  3 are on the local IDE control (yes, 2 drives share an IDE bus), and two are on an older Promise Controller.  This is what I get for speeds:

mythbackend raid5 # dd if=/dev/zero of=testfile bs=1M count=16384
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 859.12 s, 20.0 MB/s
mythbackend raid5 # 

Granted, the system is running a few virtual systems as well, but none of them hits the hard drive too hard.

Gerald

----- Original Message -----
From: "Markus Schulz" <msc at antzsystem.de>
To: mythtv-users at mythtv.org
Sent: Saturday, February 16, 2008 9:38:33 AM (GMT-0600) America/Chicago
Subject: Re: [mythtv-users] Fastest RAID for HD?

Am Samstag, 16. Februar 2008 schrieb Roger Heflin:
> Markus Schulz wrote:
> > Am Freitag, 15. Februar 2008 schrieb Marc:
> > [...]
> >
> >> Don't assume people on this list are experts. Some are, some are
> >> informed users who have done research, some just make assumptions
> >> based off of one post or one article they read.
> >>
> >> >From a statistical standpoint..
> >>
> >> Raid0 would be the fastest, it is common sense. Your speed for any
> >> action would be dependent on the number of drives you had or N.
> >> However if one drive fails you lose all data.
> >>
> >> Raid3 or 5 would be the second fastest and would be safer due to
> >> the ability to continue working without loss of data if you had a
> >> single drive fail. The difference between these 2 raid types is
> >> the way they setup parity. Raid3 has a dedicated parity drive.
> >> Raid5 spreads parity across all the drives.
> >> Speed of any action on either of these raid configs would be the
> >> number of drives you had minus 1 or N-1.
> >
> > sorry but thats not true. Show me a raid5 with 5-6 drives which
> > will got
> >
> >> 300MB/s _write_ performance...
> >
> > Fastest Raid _WITH_ redundancy was raid10.
>
> The high dollar hardware raid controllers will get close to the N-1
> rate, I have benchmarked them under sustained load, but the hardware
> raid are in the $500-$1000 range, and raid10 with 6 disks will in a
> perfect world be 180-210mb/second (3 effective
> drives-60-70mb/second/drive).   

i've built a system two weeks ago with:

6 * 73Gb 15k 2.5" sas in a smart array p400 (512MB cache) for a HP dl380 
G5 system

d1:/mnt/disk2# dd if=/dev/zero of=testfile bs=1M count=16384
16384+0 Datensätze ein
16384+0 Datensätze aus
17179869184 Bytes (17 GB) kopiert, 55,6692 Sekunden, 309 MB/s

d1:/mnt/disk2# dd if=testfile of=/dev/null bs=1M
16384+0 Datensätze ein
16384+0 Datensätze aus
17179869184 Bytes (17 GB) kopiert, 56,1641 Sekunden, 306 MB/s

-- 
Markus Schulz

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