Re: Very low disk performance Highpoint 1820a

----- Original Message ----- 
From: "willem jan withagen" <wjw_at_digiware.nl>
>> If that where the case it would have been it wouldn't have been
>> 46Mb/s it would have been 543Mb/s, just tested it for you :P
>>>> I've just finished putting together a new server box spec:
>>>> Dual AMD 244, 2GB ram, 5 * Seagate SATA 400GB on a
>>>> Highpoint 1820a RAID 5 array.
>>>
>>>> 5.4-STABLE Highpoint 1820a RAID 5 ( 5 disk )
>>>> 655360000 bytes transferred in 13.348032 secs (49097875 bytes/sec)
>>>
>>> You're only transfering 640M in 2GB of RAM, big chance that you're 
>>> testing memory/buffercode-speed in stead of testing diskspeed.
> 
> Still I would argue that if you do not use a write size larger than what 
> you have as real memory, that buffering in real memory is going to play 
> a role....

I think you miss read all the details here Willem.
Original values:
Write: 150Mb/s
Read: 50Mb/s
Current value after tweeking, RAID stripe size, vfs.read_max and
MAXPHYS ( needs more testing now due to scotts warning )
Write: 150Mb/s
Read: 200Mb/s

Note: The test size was upped to 10Gb to avoid caching issues.

> Other than that I find 50Mb/s is IMHO reasonable high value for a RAID5 
> in writting. But it would require substantial more organised testing. DD 
> is nothing more than a very crude indication of what to expect in real life.

dd was uses as it is a good quick indication of baseline sequential file access
speed and as such highlighted a serious issue with the original performance.
Thanks to the input from a number of guys here this was dramatically
increased to a more reasonable value. There is potentially more headway
for improvement which is show by the software linux RAID tests but
200Mb/s read is far more acceptable from a 5 disk system than 50Mb/s
which can be obtained from a single disk.

    Steve


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