----- Original Message ---- > From: Marion Hakanson <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Cc: zfs-discuss@opensolaris.org > Sent: Friday, February 1, 2008 1:01:46 PM > Subject: Re: [zfs-discuss] Un/Expected ZFS performance? > > [EMAIL PROTECTED] said: > > . . . > > ZFS filesystem [on StorageTek 2530 Array in RAID 1+0 configuration > > with a 512K segment size] > > . . . > > Comparing run 1 and 3 shows that ZFS is roughly 20% faster on > > (unsynchronized) writes versus UFS. What's really surprising, to me at > > least, > > is that in cases 3 and 5, for example, ZFS becomes almost 400% slower on > > synchronized writes versus UFS. I realize that the ZFS-on-RAID setup has a > > "safety" penalty, but should it really be 400% slower than UFS? If not, then > > I'm hoping for suggestions on how to get some better ZFS performance from > > this setup. > > > I don't think there is any "safety penalty" for ZFS on RAID, unless you're > comparing it to ZFS on JBOD. On RAID without ZFS-level redundancy, you only > give up ZFS-level self-healing. > > The sync-write issue here is likely similar to that of an NFS server. If all > of your ZFS pools on this system are on battery-backed cache RAID (e.g. the > 2530 array), then you could safely set zfs_nocacheflush=1. If not, then > there should be a way to set the 2530 to ignore the ZFS sync-cache requests. > > Give it a try and let us all know how it affects your tests. We've got > a 2530 here doing Oracle duty, but it's so much faster than the storage > it replaced that we haven't bothered doing any performance tuning. > Marion,
Thanks for the reply. As it turns out, I think I'm going to try a different strategy. Apparently, I can make the 2530 acknowledge the "sync" requests back to the OS without causing the write cache to get flushed (which was happening by default). Setting zfs_nocacheflush=1 would, I think, accomplish the same thing (i.e. ignore sync requests) from the OS side, but this would end up being a "global" ZFS setting on the OS. The problem with the latter solution is that if I ever decided to add non-intelligent storage to the system, it wouldn't get the sync calls either. Thanks again, Bob _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
