8.2-RC1 and ZFS

[David Samms]

On 12/31/10 08:14, Anonymous wrote:
> David Samms<dsamms at nw-ds.com>  writes:
>
> [...]
>> The same test with ZFSv28 and ZFSv28 + tuning
>>
>> ZFSv28
>> ----------------------------------------------------------------------
>> dd if=/dev/zero of=big bs=1m count=6400
>> 6710886400 bytes transferred in 158.205268 secs (42418855 bytes/sec)
>>
>> OpenOffice 197sec
>> MP3 skips
>> XFCE4 popup menus took 5-15 seconds to appear
>>
>>
>> ZFSv28 + tuning
>> --vfs.zfs.txg.timeout="5"
>
> the tunable defaults to "5" in v28, see txg.c
>
>    int zfs_txg_timeout = 5;        /* max seconds worth of delta per txg */
>
>> --vfs.zfs.txg.write_limit_override=268435456
>
> No such tunable/sysctl. It was renamed to vfs.zfs.write_limit_override
> in v28 (note ".txg." absence).
>
>> --kern.maxvnodes=250000
>
>> ----------------------------------------------------------------------
>> dd if=/dev/zero of=big bs=1m count=6400
>> 6710886400 bytes transferred in 167.316444 secs (40108947 bytes/sec)
>>
>> OpenOffice 190sec
>> No MP3 skips during "dd", but one skip while OpenOffice was starting
>> XFCE4 popup menus took 2-13 seconds to appear

Thank you for the correction.  Please disregard my previous test results 
for ZFS+tuning.  Below are the corrected results:

ZFSv28 defaults +
-- vfs.zfs.write_limit_override: 268435456
-- kern.maxvnodes=250000
----------------------------------------------------------------------
dd if=/dev/zero of=big bs=1m count=6400
6710886400 bytes transferred in 254.771374 secs (26340818 bytes/sec)

OpenOffice 82sec
No Skips
menus 0-1 sec

ZFSv28 defaults +
-- vfs.zfs.write_limit_override: 1073741824
-- kern.maxvnodes=250000
----------------------------------------------------------------------
dd if=/dev/zero of=big bs=1m count=6400
6710886400 bytes transferred in 189.671025 secs (35381716 bytes/sec)

OpenOffice 190sec
No Skips
menus 0-2 sec

Setting vfs.zfs.write_limit_override: 268435456 significantly slows 
writes but make reads wonderful.  Not ideal though.  Setting 
vfs.zfs.write_limit_override: 1073741824 brings writes up to 87% of 
UFS+s and _dramatically_ improves GUI responsiveness.  Very good setting 
for an old desktop machine.  Being a ZFS novice, I would appreciate any 
links to tuning information.  The default ZFS tuning do not seem good 
for a web-server or desktop which is fine, but guiding sysadmins to 
typical settings for their application would be helpful.