On 21 maj 2010, at 00.53, Ross Walker wrote: > On May 20, 2010, at 6:25 PM, Travis Tabbal <tra...@tabbal.net> wrote: > >>> use a slog at all if it's not durable? You should >>> disable the ZIL >>> instead. >> >> >> This is basically where I was going. There only seems to be one SSD that is >> considered "working", the Zeus IOPS. Even if I had the money, I can't buy >> it. As my application is a home server, not a datacenter, things like NFS >> breaking if I don't reboot the clients is a non-issue. As long as the >> on-disk data is consistent so I don't have to worry about the entire pool >> going belly-up, I'm happy enough. I might lose 30 seconds of data, worst >> case, as a result of running without ZIL. Considering that I can't buy a >> proper ZIL at a cost I can afford, and an improper ZIL is not worth much, I >> don't see a reason to bother with ZIL at all. I'll just get a cheap large >> SSD for L2ARC, disable ZIL, and call it a day. >> >> For my use, I'd want a device in the $200 range to even consider an slog >> device. As nothing even remotely close to that price range exists that will >> work properly at all, let alone with decent performance, I see no point in >> ZIL for my application. The performance hit is just too severe to continue >> using it without an slog, and there's no slog device I can afford that works >> properly, even if I ignore performance. > > Just buy a caching RAID controller and run it in JBOD mode and have the ZIL > integrated with the pool. > > A 512MB-1024MB card with battery backup should do the trick. It might not > have the capacity of an SSD, but in my experience it works well in the 1TB > data moderately loaded range. > > Have more data/activity then try more cards and more pools, otherwise pony up > the $$$$ for a capacitor backed SSD.
It - again - depends on what problem you are trying to solve. If the RAID controller goes bad on you so that you loose the data in the write cache, your file system could be in pretty bad shape. Most RAID controllers can't be mirrored. That would hardly make a good replacement for a mirrored ZIL. As far as I know, there is no single silver bullet to this issue. /ragge _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
