[mythtv-users] OT Hardware RAID 5 Recommendations

Paul Hamm paulhamm at verizon.net
Tue Dec 12 20:11:05 UTC 2006


Interesting ran this on my machine.  See the bottom for PC specs.  The
system is running 2 instances of FAH.  Not a very consistent test.
Using a 6 Disk raid 5 array.

[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 22.3979 seconds, 47.9 MB/s

real    0m22.489s
user    0m0.004s
sys     0m4.107s
[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 36.211 seconds, 59.3 MB/s

real    0m36.599s
user    0m0.004s
sys     0m8.936s
[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 14.7471 seconds, 72.8 MB/s

real    0m15.919s
user    0m0.005s
sys     0m4.560s
[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 29.2009 seconds, 73.5 MB/s

real    0m29.520s
user    0m0.007s
sys     0m8.787s
[root at blah temp]# ls
test
[root at blah temp]# rm test
rm: remove regular file `test'? y
[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 12.9041 seconds, 83.2 MB/s

real    0m12.906s
user    0m0.004s
sys     0m4.140s
[root at blah temp]# rm test
rm: remove regular file `test'? y
[root at blah temp]# time dd if=/dev/zero of=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 30.1432 seconds, 71.2 MB/s

real    0m30.155s
user    0m0.005s
sys     0m8.379s

Box Info

[root at blah temp]# lspci -v |grep Areca
02:0e.0 RAID bus controller: Areca Technology Corp. ARC-1220 8-Port
PCI-Express to SATA RAID Controller
        Subsystem: Areca Technology Corp. ARC-1220 8-Port PCI-Express to
SATA RAID Controller

--------- Cut from proxy management server ----------
Ch01    N.A.    N.A.    N.A.
Ch02    Raid Set # 00   320.1GB         ST3320620AS
Ch03    N.A.    N.A.    N.A.
Ch04    Raid Set # 00   300.1GB         ST3300622AS
Ch05    Raid Set # 00   300.1GB         ST3300622AS
Ch06    Raid Set # 00   320.1GB         ST3320620AS
Ch07    Raid Set # 00   300.1GB         ST3300622AS
Ch08    Raid Set # 00   300.1GB         ST3300622AS
--------- Cut from proxy management server ----------

[root at blah temp]# uname -a
Linux blah.blah.blah 2.6.18-1.2239_2.fc5.cubbi_suspend2 #1 SMP Tue Nov
14 18:42:46 EST 2006 x86_64 x86_64 x86_64 GNU/Linux
[root at blah temp]# cat /proc/cpuinfo |grep AMD
vendor_id       : AuthenticAMD
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
vendor_id       : AuthenticAMD
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
[root at blah temp]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda7             17000912   9444848   6678516  59% /
tmpfs                  1027724         0   1027724   0% /dev/shm
/dev/mapper/raid_01-vault_01
                     1441843284 873764884 509485284  64% /vault/01


On Tue, 2006-12-12 at 14:25 -0500, Mike Poublon wrote:
> I'm using software raid 5 on an athlon xp 1900 using 4 120Gb IDE drives 
> and just tested the write speed in a box with 768MB of ram
> 
> # time dd if=/dev/zero of=test bs=1M count=1024
> 1024+0 records in
> 1024+0 records out
> 
> real    0m19.959s
> user    0m0.012s
> sys     0m6.716s
> 
> # time dd if=/dev/zero of=test bs=1M count=2048
> 2048+0 records in
> 2048+0 records out
> 
> real    0m42.320s
> user    0m0.040s
> sys     0m13.881s
> 
> Yeilding about 49 MB/s write
> 
> Read speeds are about 32 MB/s (using the same tests just swapping the in 
> and out parameters)
> 
> While watching the output of top, the software raid process never really 
> gets above 10%...
> 
> FYI
> 
> -Mike
> > Brett:
> >
> > Thanks, I'm looking for RAID5 which requires that a parity bit be set
> > across all of the disks.  This requires a fair bit of horsepower.
> > RAID1 is (if I remember correctly) simply a mirror, which would be a
> > waste of disk space.  On that point, I'm not sure if software RAID
> > does level 5.
> >
> > George
> >
> >   
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-- 
Paul Hamm

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