Date: Mon, 06 Nov 2017 20:23:49 +0000 From: Frank Leonhardt <frank2@fjl.co.uk> To: freebsd-hardware@freebsd.org Subject: Re: Do I need SAS drives?.. Message-ID: <5A00C4D5.2010205@fjl.co.uk> In-Reply-To: <cd7ab44859b519b9f78fa84cb43ef4ff@vvelox.net> References: <4DFBCE11-913A-4FC9-937D-463B4D49816C@aldan.algebra.com> <CAOtMX2jeUbSm535Zvd_7aHfQao-dMs5zbU0o3GRWk%2BcmW1Nq=g@mail.gmail.com> <cd7ab44859b519b9f78fa84cb43ef4ff@vvelox.net>
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On 06/11/2017 10:09, Zane C. B-H. wrote: > In my years of doing decade plus of DC work, I've seen both SAS and SATA > drives flake and render systems in operable till the offending drive is > removed. > My experience too. > For Supermicro it will vary between backplanes. > Very true indeed. If they go on or off from time to time, that's good enough. >> I'm guessing that you don't have an expander (since you only have 8 >> slots), so item 1 doesn't matter to you. I'll guess that item 3 >> doesn't matter either, or you wouldn't have asked this question. Item >> 5 can be dealt with simply by buying the higher end SATA drives. So >> item 6 is really the most important. If this system needs to have >> very high uptime and consistent bandwidth, or if it will be difficult >> to access for maintenance, then you probably want to use SAS drives. >> If not, then you can save some money by using SATA. Hope that helps. > > Actually most boxes with more than 4 slots tend to be use multipliers. > I'm more mixed on that. There are quite a few Dells with eight or twelve-slot backplanes, even if it means two HBAs. Apart from better performance, the cost of 2xHBA+backplane is bizarrely less than 1xHBA+Expander. All the Supermicros I've seen have had expanders though. > As to uptime, that is trivial to achieve with both. > > With both it is of importance of drive monitoring and regular self tests. WHS! Biggest cause of problems is discovering a flaky drive or two AFTER the redundant one has failed. I don't know what anyone else thinks, but I'm inclined to do a straightforward read of a block device rather than a ZFS scrub because (a) I think it's quicker, especially when there's not much workload; and (b) it also reads unused blocks, which are probably the majority. "Best Practice" says you should do a scrub every three months - seems way to long a gap for my liking.
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