I have a similar question, I put together a cheapo RAID with four 1TB WD Black
(7200) SATAs, in a 3TB RAIDZ1, and I added a 64GB OCZ Vertex SSD, with slice 0
(5GB) for ZIL and the rest of the SSD for cache:
# zpool status dpool
pool: dpool
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
dpool ONLINE 0 0 0
raidz1 ONLINE 0 0 0
c0t0d0 ONLINE 0 0 0
c0t0d1 ONLINE 0 0 0
c0t0d2 ONLINE 0 0 0
c0t0d3 ONLINE 0 0 0
[b] logs
c0t0d4s0 ONLINE 0 0 0[/b]
[b] cache
c0t0d4s1 ONLINE 0 0 0[/b]
spares
c0t0d6 AVAIL
c0t0d7 AVAIL
capacity operations bandwidth
pool used avail read write read write
---------- ----- ----- ----- ----- ----- -----
dpool 72.1G 3.55T 237 12 29.7M 597K
raidz1 72.1G 3.55T 237 9 29.7M 469K
c0t0d0 - - 166 3 7.39M 157K
c0t0d1 - - 166 3 7.44M 157K
c0t0d2 - - 166 3 7.39M 157K
c0t0d3 - - 167 3 7.45M 157K
c0t0d4s0 20K 4.97G 0 3 0 127K
cache - - - - - -
c0t0d4s1 17.6G 36.4G 3 1 249K 119K
---------- ----- ----- ----- ----- ----- -----
I just don't seem to be getting any bang for the buck I should be. This was
taken while rebuilding an Oracle index, all files stored in this pool. The WD
disks are at 100%, and nothing is coming from the cache. The cache does have
the entire DB cached (17.6G used), but hardly reads anything from it. I also
am not seeing the spike of data flowing into the ZIL either, although iostat
show there is just write traffic hitting the SSD:
extended device statistics cpu
device r/s w/s kr/s kw/s wait actv svc_t %w %b us sy wt id
sd0 170.0 0.4 7684.7 0.0 0.0 35.0 205.3 0 100 11 8 0 82
sd1 168.4 0.4 7680.2 0.0 0.0 34.6 205.1 0 100
sd2 172.0 0.4 7761.7 0.0 0.0 35.0 202.9 0 100
sd3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0
sd4 170.0 0.4 7727.1 0.0 0.0 35.0 205.3 0 100
[b]sd5 1.6 2.6 182.4 104.8 0.0 0.5 117.8 0 31 [/b]
Since this SSD is in a RAID array, and just presents as a regular disk LUN, is
there a special incantation required to turn on the Turbo mode?
Doesnt it seem that all this traffic should be maxing out the SSD? Reads from
the cache, and writes to the ZIL? I have a seocnd identical SSD I wanted to add
as a mirror, but it seems pointless if there's no zip to be had....
help?
Thanks,
Tracey
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