On Wed, Jun 1, 2011 at 9:17 PM, Erik Trimble <erik.trim...@oracle.com> wrote:
> Here's how you calculate (average) how long a random IOPs takes:
>
> seek time + ((60 / RPMs) / 2))]
>
> A truly sequential IOPs is:
>
> (60 / RPMs) / 2)
>
> For that series of drives, seek time averages 8.5ms (per Seagate).
>
> So, you get
>
> 1 Random IOPs takes [8.5ms + 4.13ms] = 12.6ms, which translates to 78
> IOPS
>
> 1 Sequential IOPs takes 4.13ms, which gives 120 IOPS.
Thank you. I had found the seek specification, but did not know how to
covert it to anything approaching a useful I/Ops limit.
> Note that due to averaging, the above numbers may be slightly higher or
> lower for any actual workload.
> In your case, since ZFS does write aggregation (turning multiple write
> requests into a single larger one), you might see what appears to be
> more than the above number from something like 'iostat', which is
> measuring not the *actual* writes to physical disk, but the *requested*
> write operations.
Hurmmm, I don't think that really explains what I am seeing. iostat
output for the two drives that are resilvering (yes, we had a second
failure before Oracle could get us a replacement drive, the hoops
first line support is making us hop through is amazing, in a bad way):
iostat -xn c6t5000C5001A452C72d0 c6t5000C5001A406415d0 1
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 359.7 0.3 1181.1 0.0 1.8 0.0 5.1 0 28
c6t5000C5001A406415d0
0.1 573.3 6.2 1846.8 0.0 3.0 0.0 5.2 0 45
c6t5000C5001A452C72d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 629.3 0.0 1859.7 0.0 3.0 0.0 4.7 0 53
c6t5000C5001A406415d0
0.0 581.1 0.0 1780.8 0.0 2.8 0.0 4.9 0 48
c6t5000C5001A452C72d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 855.0 0.0 3595.7 0.0 4.9 0.0 5.7 0 70
c6t5000C5001A406415d0
0.0 785.9 0.0 3487.1 0.0 5.2 0.0 6.7 0 70
c6t5000C5001A452C72d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 842.3 0.0 2709.8 0.0 4.2 0.0 5.0 0 71
c6t5000C5001A406415d0
0.0 811.3 0.0 2607.3 0.0 4.1 0.0 5.0 0 68
c6t5000C5001A452C72d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 567.0 0.0 1946.0 0.0 2.8 0.0 4.9 0 48
c6t5000C5001A406415d0
0.0 549.0 0.0 1897.0 0.0 2.7 0.0 4.9 0 48
c6t5000C5001A452C72d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 803.8 0.0 2860.6 0.0 4.7 0.0 5.8 0 72
c6t5000C5001A406415d0
0.0 798.8 0.0 2756.4 0.0 4.3 0.0 5.4 0 70
c6t5000C5001A452C72d0
and the zpool configuration:
> zpool status
pool: zpool-53
state: DEGRADED
status: One or more devices could not be opened. Sufficient replicas exist for
the pool to continue functioning in a degraded state.
action: Attach the missing device and online it using 'zpool online'.
see: http://www.sun.com/msg/ZFS-8000-2Q
scrub: resilver in progress for 16h29m, 19.17% done, 69h28m to go
config:
NAME STATE READ WRITE CKSUM
alb-ed-01 DEGRADED 0 0 0
raidz2-0 ONLINE 0 0 0
c6t5000C5001A67E217d0 ONLINE 0 0 0
c6t5000C5001A67AF9Dd0 ONLINE 0 0 0
c6t5000C5001A67AADBd0 ONLINE 0 0 0
c6t5000C5001A67A539d0 ONLINE 0 0 0
c6t5000C5001A67A099d0 ONLINE 0 0 0
c6t5000C5001A679F0Dd0 ONLINE 0 0 0
c6t5000C5001A679C5Dd0 ONLINE 0 0 0
c6t5000C5001A679B46d0 ONLINE 0 0 0
c6t5000C5001A679A09d0 ONLINE 0 0 0
c6t5000C5001A67104Ed0 ONLINE 0 0 0
c6t5000C5001A670DBEd0 ONLINE 0 0 0
c6t5000C5001A66E3DAd0 ONLINE 0 0 0
c6t5000C5001A66411Ad0 ONLINE 0 0 0
c6t5000C5001A663D19d0 ONLINE 0 0 0
c6t5000C5001A663783d0 ONLINE 0 0 0
raidz2-1 ONLINE 0 0 0
c6t5000C5001A663474d0 ONLINE 0 0 0
c6t5000C5001A65EF79d0 ONLINE 0 0 0
c6t5000C5001A65D7C0d0 ONLINE 0 0 0
c6t5000C5001A65D50Ed0 ONLINE 0 0 0
c6t5000C5001A65D000d0 ONLINE 0 0 0
c6t5000C5001A65BBD8d0 ONLINE 0 0 0
c6t5000C5001A65BA57d0 ONLINE 0 0 0
c6t5000C5001A65A0E5d0 ONLINE 0 0 0
c6t5000C5001A659F98d0 ONLINE 0 0 0
c6t5000C5001A659D5Bd0 ONLINE 0 0 0
c6t5000C5001A658E6Bd0 ONLINE 0 0 0
c6t5000C5001A657CDCd0 ONLINE 0 0 0
c6t5000C5001A657CBBd0 ONLINE 0 0 0
c6t5000C5001A6573B0d0 ONLINE 0 0 0
c6t5000C5001A6572E8d0 ONLINE 0 0 0
raidz2-2 DEGRADED 0 0 0
c6t5000C5001A656F98d0 ONLINE 0 0 0
c6t5000C5001A655093d0 ONLINE 0 0 0
spare-2 DEGRADED 0 0 2
4335891315817043040 UNAVAIL 0 0 0 was
/dev/dsk/c6t5000C5001A654417d0s0
c6t5000C5001A452C72d0 ONLINE 0 0 0 90.9G
resilvered
c6t5000C5001A653C3Dd0 ONLINE 0 0 0
c6t5000C5001A652ABEd0 ONLINE 0 0 0
c6t5000C5001A652A1Ed0 ONLINE 0 0 0
c6t5000C5001A64D042d0 ONLINE 0 0 0
c6t5000C5001A5C1D37d0 ONLINE 0 0 0
c6t5000C5001A59722Fd0 ONLINE 0 0 0
replacing-9 DEGRADED 0 0 195
c6t5000C5001A59595Ed0 FAULTED 232 437 0 too many errors
c6t5000C5001A406415d0 ONLINE 0 0 0 90.8G
resilvered
c6t5000C5001A57F715d0 ONLINE 0 0 0
c6t5000C5001A54DB0Cd0 ONLINE 0 0 0
c6t5000C5001A4836CDd0 ONLINE 0 0 0
c6t5000C5001A4737D8d0 ONLINE 0 0 0
c6t5000C5001A455E70d0 ONLINE 0 0 0
spares
c6t5000C5001A452C72d0 INUSE currently in use
c6t5000C5001A42D792d0 AVAIL
errors: No known data errors
I know that a 15 disk drive raidz2 is not the best receipe for
performance, but we needed the capacity and this is for storing the
remote backup copy of the data, so most I/O is sequential (zfs recv).
I am trying to understand what I am seeing and relate it to real world
activity (time to resilver a failed drive, for example).
--
{--------1---------2---------3---------4---------5---------6---------7---------}
Paul Kraus
-> Senior Systems Architect, Garnet River ( http://www.garnetriver.com/ )
-> Sound Coordinator, Schenectady Light Opera Company (
http://www.sloctheater.org/ )
-> Technical Advisor, RPI Players
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