Date: Wed, 24 Jul 2013 17:38:19 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Mark Felder" <feld@freebsd.org>, <freebsd-geom@freebsd.org> Subject: Re: TRIM or no TRIM? Message-ID: <BF5ECB62A4F345EEA7AF0FAEF263527B@multiplay.co.uk> References: <512DC7C043034F891F1012DA@Mail-PC.tdx.co.uk> <A34136B4528A476BB11F178D9469D7EB@multiplay.co.uk> <D6B2C9B94A5FD0E3111D83F7@Mail-PC.tdx.co.uk> <066EB1F973D44AAC951D4D47C577266F@multiplay.co.uk> <43FCB2933BDA7D36CA1719CD@Mail-PC.tdx.co.uk> <BDD072A6EA1C4AE4A7E590BB094F7C87@multiplay.co.uk> <1374679655.8934.9223372036856590361.535ACEE3@webmail.messagingengine.com> <FB1B3079D3934712BF67AB5E7B334E57@multiplay.co.uk> <1374682388.24165.9223372036856608989.3CD1F525@webmail.messagingengine.com>
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----- Original Message ----- From: "Mark Felder" <feld@freebsd.org> > On Wed, Jul 24, 2013, at 11:08, Steven Hartland wrote: >> >> Some people have said that, we've never seen it here, quite the opposite >> in fact. >> > > It's well documented. Here's a link to take you down the rabbit hole. > > http://lists.freebsd.org/pipermail/freebsd-stable/2013-February/072171.html I've seen that thread before, but it provides very little actual evidence which would mean it effects all usages. I even just tried the very test listed in Jeremy's post and I'm unable to reproduce even the slightest sutter, let alone a total I/O stall. http://lists.freebsd.org/pipermail/freebsd-fs/2011-October/012752.html Just to be clear I'm not saying there's no issue, just we've never experienced it and we use compression on a heavily used MySQL DB, our RRD processing machine and hundreds of game servers (which are highly latency sensitive). Clearly if your performing an additional translation of the data theirs going to be an CPU overhead for doing so but if said overhead is smaller that the gain in the reduction of data written or read from the device then your still going to end up with better performance with compression than without. Maybe we're lucky and our data matches the magic pattern or perhaps others are exadurating the negative effect, possibly a combination of the two I don't know ;-) Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.
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