In any event, yes, a single U320 bus can only do 320MB in aggregate, and its practical limit is around 80% of that. HP's external enclosures are not exactly notorious for being well-balanced equipment... Only one model in any given product generation will be a single-bus design, that's the economy model. On a Sun E450 with Ultra-II (40MB/sec) drives, the system backplane is engineered so that no more than 4 drives are connected to any one channel, for example. Generally speaking, the 4-disk per channel limit is sound engineering. There's also a curious effect that I've seen but can't explain where more spindles actually slows down the array drastically... I suspect if you recreate that array as RAID 50, you'd see performance gains. -Adam
Trevor Cordes trevor@tecnopolis.ca wrote:
On 2011-05-20 Kevin McGregor wrote:
When the SCSI controller BIOS is initialized, it lists all of the drives on both channels, and most of them (as I recall) are described as being set to 80 MB/s with a note that the OS will probably set
Weird, see if the SCSI BIOS setup screens let you manually select the SCSI speed. You might have to drill down to the per-drive area. I know my U320 card gives me choices.
80MB/s per drive isn't shabby, though your drives can probably push 100-150MB/s. _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
Yeah, I've read something about limiting the SCSI chain to 4 drives. Alas, not possible in my situation. 272 MB/s read from a RAID10 is possibly the practical upper limit, despite the drives being easily able to exceed that. When I'm back at work on Tuesday I'll do a couple of quick tests of the RAID5 array.
On Fri, May 20, 2011 at 5:08 PM, Adam Thompson athompso@athompso.netwrote:
In any event, yes, a single U320 bus can only do 320MB in aggregate, and its practical limit is around 80% of that. HP's external enclosures are not exactly notorious for being well-balanced equipment... Only one model in any given product generation will be a single-bus design, that's the economy model. On a Sun E450 with Ultra-II (40MB/sec) drives, the system backplane is engineered so that no more than 4 drives are connected to any one channel, for example. Generally speaking, the 4-disk per channel limit is sound engineering. There's also a curious effect that I've seen but can't explain where more spindles actually slows down the array drastically... I suspect if you recreate that array as RAID 50, you'd see performance gains. -Adam
Trevor Cordes trevor@tecnopolis.ca wrote:
On 2011-05-20 Kevin McGregor wrote:
When the SCSI controller BIOS is initialized, it lists all of the drives on both channels, and most of them (as I recall) are described as being set to 80 MB/s with a note that the OS will probably set
Weird, see if the SCSI BIOS setup screens let you manually select the SCSI speed. You might have to drill down to the per-drive area. I know my U320 card gives me choices.
80MB/s per drive isn't shabby, though your drives can probably push 100-150MB/s. _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
-
Adam Thompson -
Kevin McGregor