Date: Sun, 30 Jan 2000 20:04:18 +0000 (GMT) From: Marc Tardif <admin@wtbwts.com> To: Greg Lehey <grog@lemis.com> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: hardware vs software stripping Message-ID: <Pine.BSF.4.10.10001301938490.60474-100000@server.b0x.com> In-Reply-To: <20000131104827.A62824@freebie.lemis.com>
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On Mon, 31 Jan 2000, Greg Lehey wrote: > On Sunday, 30 January 2000 at 14:24:54 +0000, Marc Tardif wrote: > > ... > > using postgresql. The alternatives are either raid-1 which seems too > > wasteful on disks or raid-5 which provides fault tolerance. This last > > option could substituted for a tape backup and the possibility of a few > > minutes down time in case of disk failure. > > I'm not sure I understand this sentence. Are you planning to forget > RAID-5 after all and use a tape backup? For reasonably large disks, > your downtime will be measured in hours, not minutes. For a RAID-5 > array, you shouldn't get any down time. You understood correctly, but I guess you're right. From reading the dpt.com website, hardware failures are caused by hard-drives 50% of the time. Also, from one of Simon Shapiro's posting to this mailing list, I could build a raid 0+5 array which would seem to be an optimal solution for a database performing random reads and writes. Therefore, I should probably forget simply using ccd or vinum for a production system. There is another problem though, which is that I can't really have a general idea of the amount of space I'll require. Therefore, from my understanding, if I need to expand an array containing an sql db, I'll need to rebuild the whole thing after recreating a new filesystem on the new array. I'd be very relieved if there was an easier way... > > For software, I think freebsd's ccd could provide all the services > > required for very fast i/o on a straight array of disks and at a > > fraction of the cost of the raid alternative. Unfortunately, I have > > never witnessed the virtues of raid myself and I am not in a > > position to make an educated decision. I would therefore appreciate > > if someone from this mailing list could share their experience to > > help with my dilemna. > > Why do you want to use ccd and not vinum? In any case, you may find > that either are faster than the DPT controller (if you can find one; > they're no longer making them). The more I read about raid, the more I think it could be worthwhile. Although it can be expensive, I want to make sure I get what the server needs. As for getting a DPT controller, what's this about "the DPT controller" not being made anymore? I think I should be looking for something like a PM3334UW which looks like an excellent buy, even though smartraid v will be supported soon by freebsd. Thanks for the advice, much appreciated. Marc To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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