Date: Sun, 26 May 2013 20:17:49 -0500 From: Adam Vande More <amvandemore@gmail.com> To: Warren Block <wblock@wonkity.com> Cc: Erich Dollansky <erichsfreebsdlist@alogt.com>, Polytropon <freebsd@edvax.de>, "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org>, "M. V." <bored_to_death85@yahoo.com> Subject: Re: "swap" partition leads to instability? Message-ID: <CA%2BtpaK3QwWJR5F1=1p=hQHvSDXcV_vXkX5W=pbmoQGVrZu3-dA@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1305261813040.30008@wonkity.com> References: <1369558712.96152.YahooMailNeo@web165006.mail.bf1.yahoo.com> <20130526160906.4e379016@X220.ovitrap.com> <20130526113235.f5dbe768.freebsd@edvax.de> <alpine.BSF.2.00.1305261724050.29348@wonkity.com> <CA%2BtpaK106Fu0dKmR-4_e3ZjnjoMb3ZrjWEscXX99v1qj4BzCJw@mail.gmail.com> <alpine.BSF.2.00.1305261813040.30008@wonkity.com>
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On Sun, May 26, 2013 at 7:20 PM, Warren Block <wblock@wonkity.com> wrote: > Which part? This part: "Another problem with SSDs is that they can have difficulty with wear leveling." Do as I suggested and you'll get maximum life from the drive even with swap present. Even absent of best practices, SSD's in general do a great job in managing wear leveling. We're 5+ years out from crappy SSD's with dynamic wear leveling. Modern SSD's don't suffer nearly the write amplification effect of earlier drives. Also the write amplification effect only comes into play during random writes. A lot of common swap usage isn't random. All this is of course assuming we're dealing with a quality drive. If you're using a cheap Chinese knock off, all bets are off. > A FreeBSD swap partition has no way to use TRIM, so I suggest > using a swap file on top of UFS, which does support TRIM. > > Using TRIM should preserve performance better than leaving unused space and > letting the drive wear leveling algorithm move data around without the hint. Normal dynamic wear leveling on a modern SSD will be better than imposing an FS- backed swap for 4GB partion occupying a small fraction of total drive space. File backed paging imposes two sets of bottlenecks and TRIM only *helps* with one. Another part of the equation is how much is swap used. If rarely, this is a non-issue to begin with. If it's significant, any flash SSD probably isn't appropriate. Certain other SSD's are not subject to these guidelines at all. -- Adam Vande More
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