Re: Adaptec 2400A Performance
On Sat, 24 Jan 2004 19:48:15 -0800 Rishi Chopra <[EMAIL PROTECTED]> wrote: > One other (slightly lamer) question: if my device configures as da0, is > that scsi or ide? SCSI. IDE would be "ad0". -Chris ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Adaptec 2400A Performance
In the last episode (Jan 23), Rishi Chopra said: > I've run some imperical tests on the Adaptec 2400A raid controller > (results and setup can be seen here): > > http://www.ocf.berkeley.edu/~rchopra/RaidResults.html > > I was rather disappointed with the results. Can anyone suggest what > might be causing such slow disk speeds, or whether these speeds are > out of the ordinary for a 4-disk FreeBSD RAID5 installation? I have > done nothing to configure the card aside from striping the array in > BIOS; FreeBSD seems to automatically detect the disks. > > I once ran a 2-disk RAID-0 installation on Win2k which was 6-7 times > faster on sequential read/write tests (60-70MB/sec), hence my dismay. RAID-5 has to do 4 I/Os for every write, which would explain the bad write performance, but I can't explain your read performance. It's not strictly comparable, but a Raid-5 4x73gb SCSI setup using an Adaptec 3200S (128MB cache), which looks like it uses the same RAID engine and firmware as your 2400A, averages 18MB/sec writes and 50MB/sec reads. Your card configured with a RAID 0 volume should equal your w2k speeds. -- Dan Nelson [EMAIL PROTECTED] ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Adaptec 2400A Performance
Just wanted to make sure I wasn't skipping any obvious steps. One other (slightly lamer) question: if my device configures as da0, is that scsi or ide? The reason I ask is I wish to write a custom kernel, and would like to eliminate all unnecessary configurations/devices. Charles Swiger wrote: On Jan 24, 2004, at 12:51 AM, Rishi Chopra wrote: I was rather disappointed with the results. Can anyone suggest what might be causing such slow disk speeds, or whether these speeds are out of the ordinary for a 4-disk FreeBSD RAID5 installation? I have done nothing to configure the card aside from striping the array in BIOS; FreeBSD seems to automatically detect the disks. For us to be able to comment beyond generalizations, it's necessary to also benchmark how a single disk performs. I can still answer your question, though: RAID-5 is slow. RAID-5 trades availability against performance and hardware costs. With RAID-0, n drives gives n drives' worth of usable space. With RAID-5, n drives gives n-1 drives' worth of usable space. The performance is between RAID-0 and RAID-1 is comparible for large accesses. For small accesses, particularly small writes, RAID-5 performance is much worse than plain RAID-0 or a plain disk. -- Rishi Chopra http://www.ocf.berkeley.edu/~rchopra ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Adaptec 2400A Performance
On Jan 24, 2004, at 12:51 AM, Rishi Chopra wrote: I was rather disappointed with the results. Can anyone suggest what might be causing such slow disk speeds, or whether these speeds are out of the ordinary for a 4-disk FreeBSD RAID5 installation? I have done nothing to configure the card aside from striping the array in BIOS; FreeBSD seems to automatically detect the disks. For us to be able to comment beyond generalizations, it's necessary to also benchmark how a single disk performs. I can still answer your question, though: RAID-5 is slow. RAID-5 trades availability against performance and hardware costs. With RAID-0, n drives gives n drives' worth of usable space. With RAID-5, n drives gives n-1 drives' worth of usable space. The performance is between RAID-0 and RAID-1 is comparible for large accesses. For small accesses, particularly small writes, RAID-5 performance is much worse than plain RAID-0 or a plain disk. -- -Chuck ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
