Date: Sun, 8 May 2005 15:36:45 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "willem jan withagen" <wjw@digiware.nl> Cc: freebsd-current@freebsd.org Subject: Re: Very low disk performance Highpoint 1820a Message-ID: <002b01c553db$5e167340$b3db87d4@multiplay.co.uk> References: <069901c54bfd$2967ba40$7f06000a@int.mediasurface.com> <427D5AA0.1080609@withagen.nl> <002b01c553be$93a5b790$b3db87d4@multiplay.co.uk> <427E05D2.2060706@digiware.nl>
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----- Original Message -----
From: "willem jan withagen" <wjw@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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