On 19 feb 2010, at 17.35, Edward Ned Harvey wrote: > The PERC cache measurably and significantly accelerates small disk writes. > However, for read operations, it is insignificant compared to system ram, > both in terms of size and speed. There is no significant performance > improvement by enabling adaptive readahead in the PERC. I will recommend > instead, the PERC should be enabled for Write Back, and have the readahead > disabled. Fortunately this is the default configuration on a new perc > volume, so unless you changed it, you should be fine.
If I understand correctly, ZFS now adays will only flush data to non volatile storage (such as a RAID controller NVRAM), and not all the way out to disks. (To solve performance problems with some storage systems, and I believe that it also is the right thing to do under normal circumstances.) Doesn't this mean that if you enable write back, and you have a single, non-mirrored raid-controller, and your raid controller dies on you so that you loose the contents of the nvram, you have a potentially corrupt file system? /ragge _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
