Re: [MLUG] Reasonable hard disk throughput numbers?

["Mark Rages" <EMAIL:PROTECTED>]

On 4/4/06, Phillip Kelchen <EMAIL:PROTECTED> wrote:
>
> RAID is better known for read than write speeds. I don't know how fast you
> need to have the data written, but if it's really fast, you may do better to
> have a fast 15K SCSI drives. If I remember correctly, peak write speeds on a
> 147GB 15,000 RPM Maxtor Atlas were near 100MB/sec and the slowest was about
> 60-65MB/sec. If you need faster than that, you don't have much of an option
> other than putting several of those fast HDDs in an array, and so would
> getting a 3rd-party RAID controller that sits on a high-bandwidth bus like a
> 133MHz PCI-X or PCI-express x4 or x8. But that's some serious money right
> there and the gear is server-grade and not consumer-grade.
>
> A cheaper option would be to use 500GB SATA hard drives or the 74GB or 150GB
> WD Raptor 10k SATA drives, depending on how much data you need to store.
> These are a lot more affordable and will perform between your 80GB setup and
> the 15k SCSI setup but cost $150-300 per drive instead of at least twice that
> just for the HDDs and then you need at least an SCSI controller to do SCSI on
> your board and those are expensive too. Again, how fast do you need to go?
>
> Also, XFS is supposed to be the best "big file throughput" file system. Its
> only downside is that it needs to be cleanly umounted or it will become
> corrupted. So you would need a UPS or something to ensure that you can
> cleanly umount the disk if the power goes off.
>
> I hope this helps.
>
> Phillip
>

My application only generates 30 MB/s.  So what I have will probably
be fast enough for now.  But I'm trying to get a sense of what the
various throughput/$ points are. 10K SATA would be my next choice.

But I still believe two RAID0 disks should have better (theoretically,
twice) the write performance of a single disk, or a RAID1 pair.  Is
there a reason why this would not the case?

Intuitively, a higher-density (500 G) drive spinning at the same 7200
RPM as my 80 G drives should give a higher max throughput.  However,
this is not the case, according to randomly chosen datasheets.  There
is something I'm not understanding here.

About filesystems, I have benchmarked them in the past, and my
conclusion was:  When you're just writing a single file full of 10
gigs of zeroes, the filesystem doesn't matter. It's when you have a
lot of bitty files that the filesystem design choices start to become
apparent.  For this application, I'm not running a mail server or
compiling the kernel, I'm storing huge video files.

Regards,
Mark
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