Discussion:
ZFS and Direct I/O
(too old to reply)
Heinz Müller
2009-05-10 17:40:07 UTC
Permalink
Hi,

after I got the information that ZFS ist not supported with raw devices
does anyone know if ZFS with file systems as database devices is supported with Direct I/O?

Today I've got a SYBASE newsletter with a PDF called
"Performance on SYBASE Decices Using Direct I/O, Dsync and Raw Partitions"
and it seems that database devices with Direct I/O is as fast as raw devices.

So I ask myself to use ZFS with filesystem as database devices and Direct I/O.

Thanks!

Heinz
Rob V [Sybase]
2009-05-10 22:48:38 UTC
Permalink
ZFS does not support directIO, meaning that you'll have to use dsync=true.
As for raw devices, ZFS does provide these, albeit by emulating them; the
big downside is that only synchronous I/O is supported on these.
All in all, ZFS, either as raw devs or files, is not well-suited for using
with databases since there tends to be a performance hit. UFS files (with
directIO) or real raw devices are a better choice.

HTH,

Rob V.
-----------------------------------------------------------------
Rob Verschoor

Certified Sybase Professional DBA for ASE 15.0/12.5/12.0/11.5/11.0
and Replication Server 15.0.1/12.5 // TeamSybase

Author of Sybase books (order online at www.sypron.nl/shop):
"Tips, Tricks & Recipes for Sybase ASE" (ASE 15 edition)
"The Complete Sybase ASE Quick Reference Guide"
"The Complete Sybase Replication Server Quick Reference Guide"

mailto:***@YOUR.SPAM.sypron.nl.NOT.FOR.ME
http://www.sypron.nl
Sypron B.V., Amersfoort, The Netherlands
Chamber of Commerce 27138666
-----------------------------------------------------------------
Post by Heinz Müller
Hi,
after I got the information that ZFS ist not supported with raw devices
does anyone know if ZFS with file systems as database devices is supported with Direct I/O?
Today I've got a SYBASE newsletter with a PDF called
"Performance on SYBASE Decices Using Direct I/O, Dsync and Raw Partitions"
and it seems that database devices with Direct I/O is as fast as raw devices.
So I ask myself to use ZFS with filesystem as database devices and Direct I/O.
Thanks!
Heinz
Heinz Müller
2009-05-11 16:27:18 UTC
Permalink
Post by Rob V [Sybase]
ZFS does not support directIO, meaning that you'll have to use dsync=true.
As for raw devices, ZFS does provide these, albeit by emulating them; the big downside is that only synchronous I/O is
supported on these.
All in all, ZFS, either as raw devs or files, is not well-suited for using with databases since there tends to be a
performance hit. UFS files (with directIO) or real raw devices are a better choice.
HTH,
Rob V.
Rob,

thank you. I got a similiar info from SYBASE today. I'll use SDS/LVM.

Heinz
Eugene
2009-10-07 22:13:53 UTC
Permalink
Rob,

Did something change since then, particularly ASE 15.0.3 ESD#2 and
new Solaris 10 versions ? Our sysadmin want to setup ZFS and all
what I have found (inc.solved cases) related ~ 6 months ago.


Regards,
Eugene
Post by Rob V [Sybase]
ZFS does not support directIO, meaning that you'll have to use dsync=true.
As for raw devices, ZFS does provide these, albeit by emulating them; the
big downside is that only synchronous I/O is supported on these.
All in all, ZFS, either as raw devs or files, is not well-suited for using
with databases since there tends to be a performance hit. UFS files (with
directIO) or real raw devices are a better choice.
HTH,
Rob V.
-----------------------------------------------------------------
Rob Verschoor
Certified Sybase Professional DBA for ASE 15.0/12.5/12.0/11.5/11.0
and Replication Server 15.0.1/12.5 // TeamSybase
"Tips, Tricks & Recipes for Sybase ASE" (ASE 15 edition)
"The Complete Sybase ASE Quick Reference Guide"
"The Complete Sybase Replication Server Quick Reference Guide"
http://www.sypron.nl
Sypron B.V., Amersfoort, The Netherlands
Chamber of Commerce 27138666
-----------------------------------------------------------------
Post by Heinz Müller
Hi,
after I got the information that ZFS ist not supported with raw devices
does anyone know if ZFS with file systems as database devices is supported
with Direct I/O?
Today I've got a SYBASE newsletter with a PDF called
"Performance on SYBASE Decices Using Direct I/O, Dsync and Raw Partitions"
and it seems that database devices with Direct I/O is as fast as raw devices.
So I ask myself to use ZFS with filesystem as database devices and Direct I/O.
Thanks!
Heinz
Rob V [ Sybase ]
2009-10-10 14:46:13 UTC
Permalink
Not that I'm aware of...

HTH,

Rob V.
-----------------------------------------------------------------
Rob Verschoor

Certified Sybase Professional DBA for ASE 15.0/12.5/12.0/11.5/11.0
and Replication Server 15.0.1/12.5 // TeamSybase

Author of Sybase books (order online at www.sypron.nl/shop):
"Tips, Tricks & Recipes for Sybase ASE" (ASE 15 edition)
"The Complete Sybase ASE Quick Reference Guide"
"The Complete Sybase Replication Server Quick Reference Guide"

mailto:***@YOUR.SPAM.sypron.nl.NOT.FOR.ME
http://www.sypron.nl
Sypron B.V., Amersfoort, The Netherlands
Chamber of Commerce 27138666
-----------------------------------------------------------------
Post by Eugene
Rob,
Did something change since then, particularly ASE 15.0.3 ESD#2 and
new Solaris 10 versions ? Our sysadmin want to setup ZFS and all
what I have found (inc.solved cases) related ~ 6 months ago.
Regards,
Eugene
Post by Rob V [Sybase]
ZFS does not support directIO, meaning that you'll have to use dsync=true.
As for raw devices, ZFS does provide these, albeit by emulating them; the
big downside is that only synchronous I/O is supported on these.
All in all, ZFS, either as raw devs or files, is not well-suited for
using with databases since there tends to be a performance hit. UFS files
(with directIO) or real raw devices are a better choice.
HTH,
Rob V.
-----------------------------------------------------------------
Rob Verschoor
Certified Sybase Professional DBA for ASE 15.0/12.5/12.0/11.5/11.0
and Replication Server 15.0.1/12.5 // TeamSybase
"Tips, Tricks & Recipes for Sybase ASE" (ASE 15 edition)
"The Complete Sybase ASE Quick Reference Guide"
"The Complete Sybase Replication Server Quick Reference Guide"
http://www.sypron.nl
Sypron B.V., Amersfoort, The Netherlands
Chamber of Commerce 27138666
-----------------------------------------------------------------
Post by Heinz Müller
Hi,
after I got the information that ZFS ist not supported with raw devices
does anyone know if ZFS with file systems as database devices is
supported with Direct I/O?
Today I've got a SYBASE newsletter with a PDF called
"Performance on SYBASE Decices Using Direct I/O, Dsync and Raw Partitions"
and it seems that database devices with Direct I/O is as fast as raw devices.
So I ask myself to use ZFS with filesystem as database devices and Direct I/O.
Thanks!
Heinz
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