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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.rmit.EDU.AU!news.unimelb.EDU.AU!munnari.OZ.AU!news.mel.connect.com.au!news.mira.net.au!inquo!news.seinf.abb.se!nooft.abb.no!Norway.EU.net!nntp.uio.no!nntp-oslo.UNINETT.no!nntp-trd.UNINETT.no!not-for-mail From: sthaug@nethelp.no (Steinar Haug) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Fastest sustained SCSI disk speed Date: 20 Jun 1996 07:42:44 GMT Organization: Nethelp Consulting, Trondheim, Norway Lines: 44 Message-ID: <4qavdk$ave@verdi.nethelp.no> References: <4qaih1$ave@lastactionhero.rs.itd.umich.edu> NNTP-Posting-Host: trane.uninett.no In-reply-to: pha@monkey.org's message of 20 Jun 1996 04:02:40 GMT [Paul H. Anderson] | I need to obtain rotational scsi drives that have the fastest possible | sustained throughput through the FreeBSD filesystem (bsd ffs). Cost is | not a concern, but I can't use RAM based drives, since I'd rather just | put the RAM in with the CPU. Besides, I need the drives to act as cache | for about 4-15GB of data, which means RAM drives are out of the question. | | I am planning on using an Adaptec Ultra Wide dual bus PCI controller card | (3940UW, I think). I just looked at the code, and it appears to support | this card. | | Is there a single SCSI drive that I can likely get greater than 10MB/second | sequential reads through the filesystem sustained? Is there a better card | than the adaptec? You might be able to get close on the outer tracks of a Seagate Barracuda 9. It's always helpful to look at the physical limitations of the actual disks. A Seagate Barracuda 4 (ST15150) has 74900 bytes/track on the outer cylinders, and 49350 bytes/track on the inner cylinders. With 120 rotations per second, the maximum sustained, *raw* data rate is: 74900*120 = 8988000 bytes/s on the outer cylinders 49350*120 = 5922000 bytes/s on the outer cylinders There is always some overhead, which means that the maximum sustained data rate a user will see is lower than this. For comparison, I've been able to get 7130000 bytes/s (6.8 MByte/s) sustained read speed on a Barracuda 4, on a Pentium 133 box with either NCR 53c810 (Asus SC-200) or Adaptec 2940UW, through the raw device. Speed through the filesystem was somewhat lower, but not much. A Seagate Barracuda 9 (ST19171) has 111460 bytes/track (outer cylinders) to 70830 bytes/track (inner cylinders), giving a maximum sustained raw data rate of 111460*120 = 13375200 bytes/s on the outer cylinders 70830*120 = 8499600 bytes/s on the outer cylinders So it's physically impossible to get 10 MByte/s sustained on the Barracuda 4, but it might be possible on the Barracuda 9. Steinar Haug, Nethelp consulting, sthaug@nethelp.no