Hi,
I'm using several FreeBSD zfs installations as the iSCSI production systems, they basically consist of an LSI HBA, and a JBOD with a bunch of SSD disks (12-24, Intel, Toshiba or Sandisk (avoid Sandisks btw)). And I observe a problem very often: gstat shows 20-30% of disk load, but the system reacts very slowly: cloning a dataset takes 10 seconds, similar operations aren't lightspeeding too. To my knowledge, until the disks are 90-100% busy, this shouldn't happen. My systems are equipped with 32-64 gigs of RAM, and the only tuning I use is limiting the ARC size (in a very tender manner - at least to 16 gigs) and playing with TRIM. The number of datasets is high enough - hundreds of clones, dozens of snapshots, most of teh data ovjects are zvols. Pools aren't overfilled, most are filled up to 60-70% (no questions about low space pools, but even in this case the situation is clearer - %busy goes up in the sky).
So, my question is - is there some obvious zfs tuning not mentioned in the Handbook ? On the other side - handbook isn't much clear on how to tune zfs, it's written mostly in the manner of "these are sysctl iods you can play with". Of course I have seen several ZFS tuning guides. Like Opensolaris one, but they are mostly file- and application-specific. Is there some special approach to tune ZFS in the environment with loads of disks ? I don't know.... like tuning the vdev cache or something simllar. ?
Thanks. Eugene. _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
