Date: Sat, 16 Jul 2005 15:33:51 -0500 From: Nikolas Britton <nikolas.britton@gmail.com> To: Chuck Swiger <cswiger@mac.com> Cc: FreeBSD - Questions <freebsd-questions@freebsd.org> Subject: Re: RAID Level 55 Message-ID: <ef10de9a05071613334e50bf6@mail.gmail.com> In-Reply-To: <42D9249A.2050007@mac.com> References: <ef10de9a0507160019499517ab@mail.gmail.com> <42D9249A.2050007@mac.com>
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On 7/16/05, Chuck Swiger <cswiger@mac.com> wrote: > Nikolas Britton wrote: > > I was reading on wikipedia about RAIDs trying to pass the time and I > > was thinking why not have RAID 5+5 or 5+5+5 levels, sure you waste > > 2/3th's of your space but wouldn't this be a killer setup for a > > directory server where fast reads are of the utmost importance? >=20 > Actually, no. RAID-5 prioritizes cost and reliability at the expense of > performance. RAID-5 does adequate for read-mostly volumes with big files= , and > does worst with lots of writes to small files. Ok then, a public FTP server... It doesn't matter, when your have a 405,000 RPM drive (27 drives * 15k rpm) you can do just about anything, but it would excel for data reads and especially random data reads. >=20 > RAID-5,0 or -1,0 would be a much better choice. >=20 > > Would you add up the transfer rates for each drive to get the total > > transfer rate of the array?, if true you could easily saturate a 10 > > gigabit ethernet connection with a 555 array of IDE or SATA drives. >=20 > Nope. Most machines are limited by their PCI bus and chipset to less tha= n > 1Gb/s of backplace bandwidth, although the higher-end boxes with multiple= PCI > busses or PCIe will do better. Yes I realize that the PCI bus is limited to a maximum of 260MB/s (32-bit @ 66MHz) but PCI-X @ 133MHz is 1060MB/s.... Anyways... I was just thinking out loud if there would be a useful purpose for this type of RAID array, I was bored because I had to wait for ethereal to build and then I had to wait till 3am, to do something, before I could go to sleep for the night.
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