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Full Discussion: How to measure IOPS?
Operating Systems Solaris How to measure IOPS? Post 302947623 by achenle on Friday 19th of June 2015 03:33:52 PM
Old 06-19-2015
Have you bought the storage yet? If so, what are the physical disks?

Because 7,000 IO ops/sec w/ a 20 ms response time is not an easy goal easy to meet.

And how is that 20 ms defined? Average response time or max response time?

---------- Post updated at 03:33 PM ---------- Previous update was at 03:24 PM ----------

Quote:
Originally Posted by jim mcnamara
...

I suspect you do not have a problem - check first. I also hope you did not order the NAS hardware - sounds like it was thrown at you.
Except that there are so many ways for someone not familiar with doing high-performance IO to ruin performance.

Such as "Let's set up a 27-disk RAID-6 array with a 1 MB block size per disk! Because bigger is faster!"

Then the array gets partitioned out into 34 different LUNs, so that every server in the data center has its IO contending with every other server in the data center over the same physical disks. And then wonder why the critical app they're running - that does IO via 17 layers of C++ iostreams and winds up doing 4 kb random writes all over the place because some developer whose only tool is to write more and more code reinvented the concept of a "database" but has no clue how to do it competently - is slow.

(And 4 years later only one server is left using a single LUN on that array because everyone bailed on it because performance stunk on the expensive hardware that was supposed to fix all their storage issues, but no one can figure out a good way to migrate that last server off it - and hey, it seems to be working just fine now...)

Last edited by achenle; 06-19-2015 at 04:39 PM..
 

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CCD(4)							   BSD Kernel Interfaces Manual 						    CCD(4)

NAME
ccd -- Concatenated disk driver SYNOPSIS
pseudo-device ccd [count] DESCRIPTION
The ccd driver provides the capability of combining one or more disks/partitions into one virtual disk. This document assumes that you're familiar with how to generate kernels, how to properly configure disks and pseudo-devices in a kernel con- figuration file, and how to partition disks. Note that the 'raw' partitions of the disks must not be combined. Each component partition should be offset at least one cylinder from the beginning of the component disk. This avoids potential conflicts between the component disk's disklabel and the ccd's disklabel. The kernel will only allow component partitions of type FS_CCD. But for now, it allows partition of all types since some port lacks support of an on- disk BSD disklabel. The partition of FS_UNUSED may be rejected because device driver of component disk will refuse it. In order to compile in support for the ccd, you must add a line similar to the following to your kernel configuration file: pseudo-device ccd 4 # concatenated disk devices The count argument is how many ccds memory is allocated for at boot time. In this example, no more than 4 ccds may be configured. A ccd may be either serially concatenated or interleaved. To serially concatenate the partitions, specify the interleave factor of 0. If a ccd is interleaved correctly, a ``striping'' effect is achieved, which can increase performance. Since the interleave factor is expressed in units of DEV_BSIZE, one must account for sector sizes other than DEV_BSIZE in order to calculate the correct interleave. The kernel will not allow an interleave factor less than the size of the largest component sector divided by DEV_BSIZE. Note that best performance is achieved if all component disks have the same geometry and size. Optimum striping cannot occur with different disk types. Also note that the total size of concatenated disk may vary depending on the interleave factor even if the exact same components are concate- nated. And an old on-disk disklabel may be read after interleave factor change. As a result, the disklabel may contain wrong partition geometry and will cause an error when doing I/O near the end of concatenated disk. There is a run-time utility that is used for configuring ccds. See ccdconfig(8) for more information. WARNINGS
If just one (or more) of the disks in a non-mirrored ccd fails, the entire file system will be lost. FILES
/dev/{,r}ccd* ccd device special files. SEE ALSO
config(1), MAKEDEV(8), ccdconfig(8), fsck(8), mount(8), newfs(8) HISTORY
The concatenated disk driver was originally written at the University of Utah. BSD
March 5, 2004 BSD
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