Date: Wed, 6 Aug 2008 20:07:11 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-fs@FreeBSD.ORG Subject: Re: ZFS hang issue and prefetch_disable - UPDATE Message-ID: <200808061807.m76I7BUj004737@lurza.secnetix.de> In-Reply-To: <20080806112944.6793fc11@twoflower.in.publishing.hu>
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CZUCZY Gergely wrote: > The thing, that it works on pointyhat, and it works on kris@'s box, is just an > IWFM-level, not the proof of any stability, reliability. You cannot "prove" stability or reliability. If you think you can, please tell me how. > No matter how much someone tunes ZFS, no matter what you disable, it's not > garanteed, [...] You want a guarantee? There is none. Not for ZFS, not for UFS, not for any other file system on any operating system, be it commercial or open-source. I agree that ZFS still has problems, especially related to kernel memory. AFAIK this is being worked on, and Pawel's latest patches seem to improve things a lot. Note that the ZFS code is still considered experimental (you've seen the fat warning, I assume), so it's reasonable to expect that it doesn't provide production-quality yet. It is rather totally unreasonable to expect a port of ZFS to appear in FreeBSD and be bug-free and without problems from day one. Also note that, in earlier days, certain UFS-features such as soft-updates and dirhash were also known to need a lot of memory (well, "a lot" by standards as of those days), and it's still wise to disable them on small embedded boxes with limited RAM. The memory requirements of ZFS aren't that much different, although on a larger scale. Alan Cox has worked on the problem and lifted the existing kmem limit for amd64 in FreeBSD -current. (I'm not sure if he will MFC that to 7-stable.) If you run with that code *and* Pawels latest ZFS patches, you should be a lot less likely to see the dreaded kmem panics. And that's without any tuning. Of course it might still make sense to tune ZFS for your workload in order to get better performance (e.g. disable prefetch etc.). Just the same as UFS. > Many of us has reported this, bot noone looked into it. That's completely untrue. Some people put a lot of time and efforts in FreeBSD's ZFS port. Please don't insult them. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "C++ is over-complicated nonsense. And Bjorn Shoestrap's book a danger to public health. I tried reading it once, I was in recovery for months." -- Cliff Sarginson
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