Axel Rau wrote: > > Am 05.10.2009 um 23:44 schrieb Karl Denninger: > >> Turn on softupdates. Fsck is deferred and the system comes up almost >> instantly even with TB-sized partitions; the fsck then cleans up the >> cruft. > Last time, I checked, there was a issue with background-fsck. > I will give it a chance with my new 8.0 box. > Do you have any experience with SSDs w/o BBUed Raidcontroller? > Are they fast enough to ensure flash write out of drive cache at power > failure after fsync ack? > > Axel > --- > axel.rau@xxxxxxxxx PGP-Key:29E99DD6 +49 151 2300 9283 computing @ > chaos claudius IMHO use the right tools for the job. In a DBMS environment where data integrity is "the deal" this means a BBU'd RAID adapter. SSDs have their own set of issues, at least at present..... For data that is read-only (or nearly-so) and of size where it can fit on a SSD they can provide VERY significant performance benefits, in that there is no seek or latency delay. However, any write-significant application is IMHO still better-suited to rotating media at present. This will change I'm sure, but it is what it is as of this point in time. I have yet to run into a problem with background-fsck on a softupdate-set filesystem. In theory there is a potential issue with drives that make their own decision on write-reordering; in practice on a DBMS system you run with a BBU'd RAID controller and as such the controller and system UPS should prevent this from being an issue. One of the potential issues that needs to be kept in mind with any critical application is that disks that have "intelligence" may choose to re-order writes. This can bring trouble (data corruption) in any application where a drive claims to have committed a block to stable storage where in fact it only has it in its buffer RAM and has not written it to a platter yet. The only reasonable solution to this problem is to run backed-up power so as to mitigate the risk of power disappearing at an inopportune time. Backed-up power brings other advantages as well (as a quality UPS usually comes with significant filtering and power conditioning) which refuses the up front risk of failures and is thus IMHO mandatory for any system that carries data you care about. -- Karl
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