I know adding ccd/vinum to the equation will lower my IO throughput, but the question is... if I have an external hardware shelf with 3.5TB (16 250GB drives w/ Raid 5 from hardware) and I put a Raid 0 stripe across 3 of these shelves what would my expected loss of IO be?
Thanks, Max -----Original Message----- From: Poul-Henning Kamp [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 1:02 PM To: Max Clark Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: Re: FW: 20TB Storage System In message <[EMAIL PROTECTED]>, "Max Clark" writ es: >Given the above: >1) What would my expected IO be using vinum to stripe the storage enclosures >detailed above? That depends a lot on the applications I/O pattern, an I doubt a precise prediction is possible. In particular the FibreChannel is hard to predict the throughput off because the various implementations seems to have each their own peculiar quirks performance wise. On a SEAGATE ST318452 disks, I see sequential transfer rates at the outside rim of the disk of 58MB/sec. If I stripe two of them them with CCD I get 107MB/sec. CCD has a better performance than Vinum where they compare. RAID-5 and striping a large number of disks does not scale linearly performance wise, in particular you _may_ see your average access time drop somewhat, but there is by far no guarantee that it will be better than the individual drive. >2) What is the maximum size of a filesystem that I can present to the host >OS using vinum/ccd? Am I limited anywhere that I am not aware of? Good question, I'm not sure we currently know the exact barrier. >3) Could I put all 20TB on one system, or will I need two to sustain the IO >required? Spreading it will give you more I/O bandwidth. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
