Coss Posted September 20, 2003 Report Share Posted September 20, 2003 Can any one tell me why, when I stripe two external firewire hard disks (fire wire 400, seagate 120Gb 7200 rpm 8Mb buffer), the read write seems to be equivalent to an unstriped drive? From a Tibook 667 MHz Cheers Coss Link to comment Share on other sites More sharing options...
think_too_mut Posted September 20, 2003 Report Share Posted September 20, 2003 >Can any one tell me why, when I stripe two external firewire hard disks (fire wire 400, seagate 120Gb 7200 rpm 8Mb buffer), the read write seems to be equivalent to an unstriped drive? You did not say much about the environment. Striping will give you better performance only if the stripes are seen through different SCSI channels. In other words, two drives have to be in the same device group that has striping configured but connected to separate SCSI channels. Link to comment Share on other sites More sharing options...
BritTim Posted September 21, 2003 Report Share Posted September 21, 2003 Unfortunately, while firewire drives (in practice) perform better than USB2 drives, the firewire interface itself is still the bottleneck. I am interested in knowing all the details of why myself (any experts on this?) but it seems that I/O processing over firewire requires help from the software drivers and, thus, relies on gaining control of the CPU. The average time this takes depends on the operating system but always seems to restrict the number of I/Os per second that can be processed. Thus, while the maximum transfer speed is 400MBPS, most of the time is spent waiting for the software driver to do its bit and the maximum actually achieved is much less. Assuming your firewire drives are on the same bus, you will achieve no performance gain from RAID. Link to comment Share on other sites More sharing options...
think_too_mut Posted September 22, 2003 Report Share Posted September 22, 2003 >Assuming your firewire drives are on the same bus, you will achieve no performance gain from RAID. And if you are doing RAID through software, you may even lose on performance. At this stage, FireWire is still in the domain of hobby electronics, nothing robust in there as in good old SCSI. Link to comment Share on other sites More sharing options...
Coss Posted September 23, 2003 Author Report Share Posted September 23, 2003 Gentlemen, thank you. SCSI is out of my league unfortunately, too expensive. Thanks TTM BritTim, you've given me the answer, Oh well! Mac OSX 10.2.8, 400 firewire and a Tibook 667Mhz It's what I do my video editing on. The bare minimum I'm afraid. PB 17" 1.33 Ghz on the shopping list, or maybe a G5. Cheers Coss :up: Link to comment Share on other sites More sharing options...
adikgede Posted September 25, 2003 Report Share Posted September 25, 2003 I'm not sure how much a G5 would help in the RAID department, because it looks like it only has room for two drives. I think they want people to buy NAS units, another USD2,000 and way up. For the average user Having faster fire wire, and Serial ATA should help though, as well as having /usr/lib /var and <swap> on seperate disks. Link to comment Share on other sites More sharing options...
Coss Posted September 25, 2003 Author Report Share Posted September 25, 2003 I spoke to a more techhy person than I today and he was of the opinion that there should be a vast improvement and that the hard disks were capable of 10 x more. I think it must be me Tibook 667, they had to replace the board and I think I've got less firewire speed now than before, oh well. This book has had one new screen, one new board, one new painted surround but the hard disk and keyboard are original. Just ordered a 17" 133 Ghz Cheers Coss Link to comment Share on other sites More sharing options...
Coss Posted September 25, 2003 Author Report Share Posted September 25, 2003 Says adikgede: as well as having /usr/lib /var and <swap> on seperate disks. Hi Adik, can you explain this to me and how to achieve it? Cheers Coss Link to comment Share on other sites More sharing options...
BritTim Posted September 25, 2003 Report Share Posted September 25, 2003 My expectation would be that serial ATA would provide greatly improved harddrive performance compared to IEEE1394 because the data can be moved directly into memory assynchronous to CPU activity and without the need for processing of interrupts. Anyone know different? Link to comment Share on other sites More sharing options...
adikgede Posted September 25, 2003 Report Share Posted September 25, 2003 Sorry I can't. [ibook2:~/] adikgede% cat /etc/fstab.hd # This file is obsolete /dev/hd0a / ufs rw 1 1 /dev/hd0e /var ufs rw 1 2 /dev/hd0f /usr ufs rw 1 2 /dev/hd0d /tmp mfs rw,-s=12000,-b=8192,-f=1024,-T=sd660 0 0 It looks like Apple put their files system table some where else. This is just a place holder. You should talk with the vendor for your app about maximizing I/O, failing that ask around at the Mac OS X Hints forum. Link to comment Share on other sites More sharing options...
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