On Mar 20, 2008, at 2:00 PM, Bob Friesenhahn wrote:
> On Thu, 20 Mar 2008, Jonathan Edwards wrote:
>>
>> in that case .. try fixing the ARC size .. the dynamic resizing on
>> the ARC
>> can be less than optimal IMHO
>
> Is a 16GB ARC size not considered to be enough? ;-)
>
> I was only describin
> Is a 16GB ARC size not considered to be enough? ;-)
>
> I was only describing the behavior that I observed. It seems to me
> that when large files are written very quickly, that when the file
> becomes bigger than the ARC, that what is contained in the ARC is
> mostly stale and does not help m
On Thu, 20 Mar 2008, Jonathan Edwards wrote:
>
> in that case .. try fixing the ARC size .. the dynamic resizing on the ARC
> can be less than optimal IMHO
Is a 16GB ARC size not considered to be enough? ;-)
I was only describing the behavior that I observed. It seems to me
that when large fil
On Mar 20, 2008, at 11:07 AM, Bob Friesenhahn wrote:
> On Thu, 20 Mar 2008, Mario Goebbels wrote:
>
>>> Similarly, read block size does not make a
>>> significant difference to the sequential read speed.
>>
>> Last time I did a simple bench using dd, supplying the record size as
>> blocksize to it
On Thu, 20 Mar 2008, Mario Goebbels wrote:
>> Similarly, read block size does not make a
>> significant difference to the sequential read speed.
>
> Last time I did a simple bench using dd, supplying the record size as
> blocksize to it instead of no blocksize parameter bumped the mirror pool
> sp
> Similarly, read block size does not make a
> significant difference to the sequential read speed.
Last time I did a simple bench using dd, supplying the record size as
blocksize to it instead of no blocksize parameter bumped the mirror pool
speed from 90MB/s to 130MB/s.
-mg
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Hello Bob,
Wednesday, March 19, 2008, 11:23:58 PM, you wrote:
BF> On Wed, 19 Mar 2008, Bill Moloney wrote:
>> When application IO sizes get small, the overhead in ZFS goes
>> up dramatically.
BF> Thanks for the feedback. However, from what I have observed, it is
BF> not a full story at all.
> On my own system, when a new file is
> written, the write block size does not make
> a significant difference to the write speed
Yes, I've observed the same result ... when a new file is being written
sequentially, the file data and newly constructed meta-data can be
built in cache and writt
On Wed, 19 Mar 2008, Bill Moloney wrote:
> When application IO sizes get small, the overhead in ZFS goes
> up dramatically.
Thanks for the feedback. However, from what I have observed, it is
not a full story at all. On my own system, when a new file is
written, the write block size does not m
Hi Bob ... as richard has mentioned, allocation to vdevs
is done in a fixed sized chunk (richard specs 1MB, but I
remember a 512KB number from the original spec, but this
is not very important), and the allocation algorithm is
basically doing load balancing.
for your non-raid pool, this chunk size
On Sun, 16 Mar 2008, Richard Elling wrote:
>
> But where is the bottleneck? iostat will show bottlenecks in the
> physical disks and channels. vmstat or mpstat will show the
> bottlenecks in cpus. To see if the app is the bottleneck will
> require some analysis of the app itself. Is it spending
Bob Friesenhahn wrote:
> On Sat, 15 Mar 2008, Richard Elling wrote:
>>
>> My observation, is that each metaslab is, by default, 1 MByte in
>> size. Each
>> top-level vdev is allocated by metaslabs. ZFS tries to allocate a
>> top-level
>> vdev's metaslab before moving onto another one. So you s
> I do see that all the devices are quite evenly busy. There is no
> doubt that the load balancing is quite good. The main question is if
> there is any actual "striping" going on (breaking the data into
> smaller chunks), or if the algorithm is simply load balancing.
> Striping trades IOPS f
On Sat, 15 Mar 2008, Richard Elling wrote:
>
> My observation, is that each metaslab is, by default, 1 MByte in size. Each
> top-level vdev is allocated by metaslabs. ZFS tries to allocate a top-level
> vdev's metaslab before moving onto another one. So you should see eight
> 128kByte allocs per
Bob Friesenhahn wrote:
> Can someone please describe to me the actual underlying I/O operations
> which occur when a 128K block of data is written to a storage pool
> configured as shown below (with default ZFS block sizes)? I am
> particularly interested in the degree of "striping" across mirr
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