Quoting Terje Elde <te...@elde.net>:
On 16. sep. 2011, at 12:31, free...@top-consulting.net wrote:
Right now I defined an entire array of 8TB ( all 16 disks )
separated in two pieces. 50 GB for FreeBSD to boot and the rest
available to configure as storage.
ZFS will want to write to it's ZIL (zfs intent log) before writing
to the final location of the data. Even if you're not waiting for
the ZIL-write to disk (because of the controller ram), those writes
will probably make it through to disk. That gives you twice as many
writes to disk, and a lot more seek.
If you want to take zfs for a proper spin, I'd like to sugget adding
two small SSDs to the setup, mirrored by zfs. You can use those both
for the ZIL, and also as cache, for the array. That's a fairly small
investment these days, and I would be surprised if it didn't
significantly improve performance, both for your benchmark, and real
load.
Note: you might be in trouble if you loose your ZIL, thus the
doubling up. I *think* you can SSD a cache without risking dataloss,
but don't take my word for it.
Terje
Well, I tried disabling the ZIL on a new dataset. These are the
commands that I ran:
zpool create data da1
zfs create data/maildomains
zfs set sync=disabled data/maildomains
dd bs=1024 if=/dev/zero of=/data/maildomains/t1 count=1M
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 14.537711 secs (73859071 bytes/sec)
Got a measly 74MB/sec.
On the UFS partition however...
dd bs=1024 if=/dev/zero of=/usr/t1 count=1M
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 5.828395 secs (184225983 bytes/sec)
184MB/sec!
And this is synchronous writing, not random!
So what is ZFS good for finally ? Synchronous writing or small random iops ?
By the way, this is how the array is configured with 3ware:
Unit UnitType Status %RCmpl %V/I/M Stripe Size(GB) Cache AVrfy
------------------------------------------------------------------------------
u0 RAID-10 OK - - 64K 7450.5 ON ON
VPort Status Unit Size Type Phy Encl-Slot Model
------------------------------------------------------------------------------
p0 OK u0 931.51 GB SATA 0 - WDC WD1002FBYS-01A6
p1 OK u0 931.51 GB SATA 1 - WDC WD1002FBYS-01A6
p2 OK u0 931.51 GB SATA 2 - WDC WD1002FBYS-01A6
p3 OK u0 931.51 GB SATA 3 - WDC WD1002FBYS-01A6
p4 OK u0 931.51 GB SATA 4 - WDC WD1002FBYS-01A6
p5 OK u0 931.51 GB SATA 5 - WDC WD1002FBYS-01A6
p6 OK u0 931.51 GB SATA 6 - WDC WD1002FBYS-01A6
p7 OK u0 931.51 GB SATA 7 - WDC WD1002FBYS-01A6
p8 OK u0 931.51 GB SATA 8 - WDC WD1002FBYS-01A6
p9 OK u0 931.51 GB SATA 9 - WDC WD1002FBYS-01A6
p10 OK u0 931.51 GB SATA 10 - WDC WD1002FBYS-01A6
p11 OK u0 931.51 GB SATA 11 - WDC WD1002FBYS-01A6
p12 OK u0 931.51 GB SATA 12 - WDC WD1002FBYS-01A6
p13 OK u0 931.51 GB SATA 13 - WDC WD1002FBYS-01A6
p14 OK u0 931.51 GB SATA 14 - WDC WD1002FBYS-01A6
p15 OK u0 931.51 GB SATA 15 - WDC WD1002FBYS-01A6
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