Messages in this thread | | | Date | Mon, 16 Feb 2004 12:18:30 -0500 | From | Timothy Miller <> | Subject | Re: File system performance, hardware performance, ext3, 3ware RA ID1, etc. |
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Daniel Blueman wrote: > Tim, > > Do you get the same numbers (but slightly higher, as this is will measure > from a smaller portion of outer zones) with: > > # hdparm -t /dev/sda > > ?
I ran this test. This is a read test. What I did below was a write test.
Additionally, I ran this test: time dd if=/dev/sda of=/dev/null bs=1024k count=1024
From that, I got 47 megs/sec. From 'hdparm -t /dev/sda', I got a slightly lower number.
So, for reads, I'm getting good performance. 47 megs/sec at the outer-most tracks is a bit lower than the 50+ that reviewers report, but it's not bad.
However, I don't get anywhere near the 40+ megs/sec the reviewers say the drive gets for writes. That model as a single drive in my wife's computer gets about 39 megs/sec, which is great. But behind the 3ware, the drive gets only 13 megs/sec. (iozone reports about 15 megs/sec, but that's influenced by caching in RAM, and iozone is writing to a file on tracks further out, I think.)
> > >>Adam Radford wrote: >> >>>Perhaps you are issuing non purely sequential IO. The card firmware >> >>does >> >>>some >>>reodering, but at some point it will cause performance degradation. Can >> >>you >> >>>try >>>kernel 2.6 w/xfs? >> >>Not any time soon, but as I mentioned earlier, I measured 13.9 megs/sec >>when I ran this command: >> >> time dd if=/dev/zero of=/dev/sda2 bs=1024k count=1024 >> >>No file system was involved; I was simply writing zeros to the block >>device (swap partition with swap off). It took 73.522 seconds to do the >>above operation. Also, I was running in single-user mode while doing >>the test. >> >> >>>Also, in my experience, the 'raw io' interface doesn't issue any >>>asynchronous IO. The >>>card _definately_ needs asynchronous IO posted to it or you will not get >>>good results >>>because you won't get all the drives busy. >> >>With RAID1, both drives will be written with the same data. There is no >>need to be asynchronous, since it's all completely linear and sequential >>with large data blocks. > >
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