Date: Sat, 28 Jul 2012 20:22:11 +0200 (CEST) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Vladimir Videscu <vladimir.videscu@gmail.com> Cc: questions@freebsd.org Subject: Re: FreeBSD on SSD Message-ID: <alpine.BSF.2.00.1207282016110.9859@wojtek.tensor.gdynia.pl> In-Reply-To: <CAMxhPysfghi-0ufy0OU0nonqha5mFeRacPVXM0MBDe6fqxmjUg@mail.gmail.com> References: <CAMxhPyt-gF228nX0DNrdsFVXKVx6YjZVa7obfov5vf%2BdtV71zw@mail.gmail.com> <alpine.BSF.2.00.1207281229260.6801@wojtek.tensor.gdynia.pl> <CAKB6gVgEyvVYaUvLkvE_AU-aViJxHAiLu6drcodLjOOBeNEYLg@mail.gmail.com> <CAMxhPysfghi-0ufy0OU0nonqha5mFeRacPVXM0MBDe6fqxmjUg@mail.gmail.com>
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> The read-cache idea is very sound, mainly because by using it this way Seagate would not have to create a special set of > instructions for installing and using the HDD. I don't think that this drive cache is smart enough to really cache needed things and not flush that cache with useless data too often. i personally would prefer that drive to show up as 8GB disk and 750 GB disk. It would be easy to fit most of /usr in 8GB with even large set of software installed. when out of space then use softlinks and move not very used things (eg. documentation, non-yours locales, examples, some linarly accessed big files etc.) to disk. > My final question would be : > > Seeing as the HDD only has a SATA connector, this would mean that the SSD part already has a memory control device that regulates > access to that sector, whether it is a plain read-cache or not. This would imply that FreeBSD could communicate with the HDD > normally, through the SATA connector, just like any regular HDD. indeed. Such a drive is a good idea, but complete lack of documentation (how it operate) is not. You have to guess how this SSD-cache works because it is not documented. the other thing is erasing data. You want to sell that drive and clear your data by dd if=/dev/zero of=/dev/disk bs=1m but does it clear SSD cache? i don't think so. Someone sophisticated enough would perform raw read of cache chips and get cached data, which can actually be the most important part (things you work on often).
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