On 25/04/2016 5:03 AM, Ralf wrote:
Some Western Digital Green stuff:
There's a big part of your problem, never ever use WD greens in
servers, especially with ZFS. They are a desktop drive, not suitable for
24/7 operation. They have power saving modes which can't be disabled and
slow them down, they don't support the ata TLER, which necessary for
prompt timing out on disk errors - greens will hang for every accessing
a bad read/write which will freeze your whole zfs pool (I've been
there). Might be worth scanning your dmesg for disk errors.
But you should really be using NAS rated drives. I thoroughly recommend
the Western Digital Reds, they aren't high performance but they are very
reliable and fast enough. For better performance (and more $) the
Hitachi NAS drives are also very good.
I had two WD Blacks start failing on me last weekend, less than a year
in the server, a tense few hours :) And one had failed earlier after 6
months. They run too hot and aren't up to the 24/7 workout they get in a
typical VM Server. We've replaced them all with WD Red (3TB) now.
What ZFS disk setup do you have? - could you post your "zpool status"
Mine are RAID10 with a ssd for log and cache.
zpool status
pool: tank
state: ONLINE
scan: resilvered 1.46T in 11h10m with 0 errors on Fri Apr 22 05:04:00
2016
config:
NAME STATE READ WRITE
CKSUM
tank ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N7XE8CXN ONLINE 0 0 0
ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N5EC7AUN ONLINE 0 0 0
mirror-1 ONLINE 0 0 0
ata-WDC_WD30EFRX-68EUZN0_WD-WMC4N0D46M4N ONLINE 0 0 0
ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N7DH176P ONLINE 0 0 0
logs
ata-Samsung_SSD_850_PRO_128GB_S24ZNSAG422885X-part1 ONLINE 0 0 0
cache
ata-Samsung_SSD_850_PRO_128GB_S24ZNSAG422885X-part2 ONLINE 0 0 0
I recommend RAID10 for performance and reduncy purposes as well. It has
twice the write IOPS and 4 times the Read IOPS of a single disk. It
outperforms raid 5 or 6 (RAIDZ, RAIDZ2)
- http://www.zfsbuild.com/2010/05/26/zfs-raid-levels/
The ssd log partition speeds up writes, the cache speeds up reads (with
time, as its get populated).
Warning: To large a cache can actually kill performance as it uses up
ZFS ARC memory.
ZFS needs RAM as well, how much have you allocated to it?
--
Lindsay Mathieson
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