Another script, which provides a missing feature to Oracle Solaris 10/11: ZFS statistics per zpool and per zone.
The ZFS in Oracle Solaris 10 and 11 is still not completely ready for a single pool setup, for some applications it makes sense to use multiple pools. In general, if one workload stresses the single zpool too much, the performance of the other workloads can be degraded. Therefore it’s still best practice to use multiple pools, for example the “Configuring ZFS for an Oracle Database” white paper suggests to use at least an own pool for the redo-logs.
The example setup
According to the white paper we use separate pools for the different workloads, an own pool for the oracle data files and an own one for the redo-logs. As we like to run more than one database on a server, the overhead would be significant if we create an own zpool for every database. Therefore we simple put every database in an own Solaris Zone (aka Container) with dedicated ZFS filesystems.
# zfs list -o name,mountpoint NAME MOUNTPOINT rpool/zones/zone1 /zones/zone1 rpool/zones/zone2 /zones/zone2 rpool/zones/zone2 /zones/zone3 data_pool/zone1 /zones/zone1/root/oradata data_pool/zone2 /zones/zone2/root/oradata data_pool/zone3 /zones/zone3/root/oradata redo_pool/zone1 /zones/zone1/root/oralogs redo_pool/zone2 /zones/zone2/root/oralogs redo_pool/zone3 /zones/zone3/root/oralogs
Imagine, the I/O performance of the database in zone2 is not as expected. You check with “iostat” and “zpool iostat” and you identify a very high load on the “data_pool” zpool. There are many different options to solve this issue, but to fully understand the problem, you very likely want to know which database is causing the high I/O. But how to identify the evil database?
If you use a smart filesystem layout (e.g. own FS per zone per database per zpool) you can use the “fsstat” utility, to get an idea of how much I/O is handled on which filesystem.
# fsstat -i `mount -p | grep zfs | cut -d' ' -f3 | tr '\n' ' '` 10 read read write write rddir rddir rwlock rwulock ops bytes ops bytes ops bytes ops ops 344K 415M 12.7K 41.9M 9.22K 2.40M 366K 366K / 3.18K 28.4M 850 495K 2.90K 4.65M 6.91K 6.91K /zones/zone1/root/oradata ...
In Solaris 11 the first awareness for zones was added, with “fsstat -i -Z zfs
If fsstat can’t help you, it’s more complicated as it should be. Therefore I wrote the following DTrace script:
#./zpool-zones-vio.d 10s zpool zonename reads reads(KB) writes writes(KB) ----- -------- ----- --------- ------ ---------- data_pool zone3 0 0 6 51 redo_pool zone3 0 0 6 51 redo_pool zone2 0 0 14 128 redo_pool zone1 0 0 26 297 rpool zone2 1 142 0 0 rpool zone3 2 174 0 0 rpool zone1 3 316 2 4 data_pool zone2 5 112 120 640 data_pool zone1 2601 1468256 500 4980
The script uses the syscall-provider, therefore the absolute values are comparable to the fsstat utility, but not to “iostat”. E.g. I/O which is only handled by the ZFS ARC cache is also counted.
Non-Oracle ZFS distributions:
Illumos based systems like SmartOS already offer a feature called “I/O Throttle” to limit the I/O caused by a zone, which tries to solve the noisy-neighbor problem. But a similar feature is not yet available for Oracle Solaris.