From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bakul Shah To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> In-reply-to: Your message of "Sat, 03 Feb 2018 18:49:50 +0000." References: <0cd144e079b9354209187e89b8a05836@quintile.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <475.1517688655.1@bitblocks.com> Content-Transfer-Encoding: quoted-printable Date: Sat, 3 Feb 2018 12:10:55 -0800 Message-Id: <20180203201110.75A91156E80B@mail.bitblocks.com> Subject: Re: [9fans] Is fossil/venti file system a good choice for SSD? Topicbox-Message-UUID: cb983b6a-ead9-11e9-9d60-3106f5b1d025 On Sat, 03 Feb 2018 18:49:50 +0000 "Digby R.S. Tarvin" wrote: Digby R.S. Tarvin writes: > = > My experience of running normal (read mostly) Linux filesystems on solid > state media is that SSD is more robust but far less reliable than rotati= ng > media. > = > MTBF for rotating media for me has been around 10 years. MTBF for SSD ha= s > been about 2. And the SSD always seems to fail catastrophically - appear= ing > to work fine one day, then after an inexplicable crash, half the media i= s > unreadable. I assume this is something to do with the wear leveling, whi= ch > successfully gets most of the blocks to wear out at the same time with n= o > warning. If I reformat and reload the SSD to correct all the mysterious > corruptions, it last a few weeks, then does the same thing again. MTTF doesn't make much sense for SSDs. A 1TB SSD I bought a couple years ago has a rating of 300 TB written, an MTBF of 2M hours and a 10 year warranty. It can do over 500MB/s of sequential writes. If I average 9.5MB/s writes, it will last year. If I continuoulsy write 100MB/s, it will last under 35 days. In contrast the life of an HDD depends on how long it has been spinning, seeks, temperature and load/unloads. A disk with 5 year warraty will likely last 5 years even if you write 100MB/s continuously. And consumer HDSC cards such as the ones used in cameras and Raspi are much much worse. In practice an SSD will last much longer than a HDD since average write rates are not high for the typical things people do.