Very low disk performance Highpoint 1820a

[Steven Hartland]

----- Original Message ----- 
From: "Scott Long" <scottl at samsco.org>
>> Ok some real strange going on write performance is ~ 140MB/s:
>> gstat:
>> dT: 0.505  flag_I 500000us  sizeof 240  i -1
>> L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
>>    0   1100      4     63   13.2   1096 140313    1.2   57.8| da0
>>    0   1100      4     63   13.3   1096 140313    1.3   59.3| da0s1
>> 
>> where as read is ~42MB/s
>> gstat:
>> dT: 0.505  flag_I 500000us  sizeof 240  i -1
>> L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
>>    1    335    335  42836    2.8      0      0    0.0   93.3| da0
>>    1    335    335  42836    2.8      0      0    0.0   93.6| da0s1
> 
> First of all, you're only sending roughly 3GB of data through.  Since
> you have 2GB of RAM, you're likely getting a lot of write caching
> from the OS.  If you want more representative numbers, either test
> with a much larger data set or with a much smaller RAM size.  Second,
> since you're going through the filesystem, there is a very good chance
> that the filesystem blocks are not aligning well with the array
> blocks.  This hurts quite a bit on any controller, and I can imagine
> it being extremely bad on a controller like this one.  Try doing your
> DD test straight to the device node.  In my local testing I was able to
> get about 400MB/sec across 6 disks in RAID-0.  RAID-5 read should
> get almost as good in a similar configuration (unless the RAID stack
> is checking parity on read, a question that I cannot answer).  I would
> expect RAID-5 write to be significantly lower due to the extra cpu and
> memory bus overhead of doing the parity calculations.  This will of
> course depend also on the speed of your drives and the speed of your PCI
> and memory bus.
> 
> The DD commands that I usually use:
> 
> dd if=/dev/zero of=/dev/da0 bs=1m
> dd if=/dev/da0 of=/dev/null bs=1m


Just retried with a ~10Gb data set:
Write to FS:
dd if=/dev/zero of=.testfile bs=1m count=10000
10000+0 records in
10000+0 records out
10485760000 bytes transferred in 92.517222 secs (113338466 bytes/sec)

Read from FS:
dd if=.testfile of=/dev/null bs=1m count=10000                  
10000+0 records in
10000+0 records out
10485760000 bytes transferred in 225.723348 secs (46454034 bytes/sec)

Read from device:
dd if=/dev/da0 of=/dev/null bs=1m count=10000
10000+0 records in
10000+0 records out
10485760000 bytes transferred in 200.723666 secs (52239779 bytes/sec)

N.B. didn't do the write to the device direct as the array is
the system drive so I don't think it would take kindly to that :)

So it doesn't seem like caching is an issue and as others are seeing
similar performance issues on other RAID controllers is could well
not be a driver issue but I'm not ruling that out as yet as it could be
the same problem in each respective driver.
So far Highpoint 1820a and 3ware ?? ( Pete can u fill in the blank here )
are exhibiting the same issue.

    Steve


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