Date: Thu, 22 Oct 2015 15:11:15 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: gjournal and TRIM: A safe combination? Message-ID: <20151022151115.33ee33f0@gumby.homeunix.com> In-Reply-To: <867fmh12nq.fsf@WorkBox.Home> References: <867fmh12nq.fsf@WorkBox.Home>
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On Tue, 20 Oct 2015 19:33:13 -0500 Brandon J. Wandersee wrote: > I've recently created several new UFS partitions on an SSD. I > activated gjournal on the largest--about 200Gb in size > 1. UFS with TRIM, but without journaling. Disk performance is > maintained, but data is unprotected in the event of a crash. UFS with soft-updates is roughly equivalent to the the metadata journalling used on most modern filesystems. Personally, I wouldn't use gjournal on an SSD for several reasons: 1. full data journalling doubles the writes with respect to basic UFS and therefore halves the life of the device. SU by contrast presumably reduces the total writes by rolling-up multiple metadata updates in memory. 2. the journal needs to be much larger than on an ordinary hard drive because of the write speeds, which is wasteful. 3. I suspect gjournal has had very little use on SSDs, so there may be SSD specific bugs. I use gjournal with large partitions on spinning disks, and soft-updates with foreground checks for my SSD and small partitions. I've never had a problem with SUs with foreground checks.
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