Hi, I think my SATA cables should be fine, as dumping from the raw block device yields to 100MiB/s. I even tried offlining one disk and then checked performance: Still bad.
But I don't get the point. If SATA cables were broken, how can I get good performance on raw block devices? Nevertheless, I have no clue what's going on, so i'll give it a try. Ralf On 04/24/2016 06:57 PM, Adam Thompson wrote: > Perhaps irrelevant, but a colleague of mine recently solved a puzzling > performance issue merely by replacing the existing SATA cables with new, > properly-rated cables. > Turns out, much like USB v1 vs USB v2, there's next to nothing distinguishing > SATA I cables vs SATA II cables vs SATA III cables, except for unusually poor > performance when used at too high a speed. > Only the magnitude of your performance drop suggests this; also the fact that > you get good raw read performance, which mirrors the symptoms in the SATA > cable case precisely. > -Adam > > On April 24, 2016 11:49:38 AM CDT, Robert Fantini <[email protected]> > wrote: >> if those are not ssd drives, then adding a zil drive will most likely >> help. >> >> On Sat, Apr 23, 2016 at 2:15 PM, Ralf <[email protected]> >> wrote: >> >>> Hi, >>> >>> I encounter very bad read/write performance on my mirror-zfs, even on >>> hypervisor-side. >>> >>> After shutting down all VMs, reading and writing from raw ZFS block >>> devices VMs runs at maximum 5MiB/s (tested with dd >>> if=/dev/rpool/VM/disk-100 of=/dev/null) while reading from the >>> underlying raw-disk (/dev/sda) has good performance (~100MiB/s). Of >>> course, performance inside VMs is even worse. Any ideas? >>> >>> This is my setup: >>> Proxmox / 4.1-30/9e199213 / Linux 4.4.6-1-pve / ZFS mirror, two disks >>> >>> ZFS setup: >>> >>> $ dmesg | grep ZFS >>> [ 2.882118] ZFS: Loaded module v0.6.5.6-1, ZFS pool version 5000, >> ZFS >>> filesystem version 5 >>> >>> $ zpool status >>> [snip] >>> NAME STATE READ WRITE CKSUM >>> rpool ONLINE 0 0 0 >>> mirror-0 ONLINE 0 0 0 >>> sdb2 ONLINE 0 0 0 >>> sda2 ONLINE 0 0 0 >>> >>> ZFS module parameters: >>> $ cat /etc/modprobe/zfs.conf >>> options zfs zfs_arc_max=3221225472 >>> >>> Partition alignement: >>> $ parted /dev/sda >>> (parted) align-check o 2 >>> 2 aligned >>> >>> Dedup: off >>> Checksumming: on >>> Compression: off >>> >>> Anything helps! >>> >>> Cheers >>> Ralf >>> _______________________________________________ >>> pve-user mailing list >>> [email protected] >>> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user >>> >> _______________________________________________ >> pve-user mailing list >> [email protected] >> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user _______________________________________________ pve-user mailing list [email protected] http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user
