'RAW DEVICE + AIO' v.s. 'JFS'
ITEM: RS4000016661
**************> QUESTION level 1 --> level 2 SPECIALIST <**************
My customer wants to know which should be used by user-applications
(like RDB), 'RAW DEVICE +AIO' or 'JFS'.
We are understanding that larger LV can be used by using 'RAWDEVICE +
AIO', however worrying about any possibilities to be lost coherences on
any accidents when using 'RAW + AIO'. My customer says that if there is
such a possibility, we shuld use 'JFS' for its better performance...
What kind of differences are there in functions beteen them exactly?
Please let me know.
Thanks a lot in advance.
**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> ASGN: AUSJZ AT WTSCPOK ======================== DATE:950821
TIME:1019
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**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> RESP: AIXOPSYS AT WTSCPOK ======================== DATE:950821
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**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> RESP: AIXOPSYS AT WTSCPOK ======================== DATE:950823
TIME:1614
Yes, you can use raw devices to get larger LVs, but if you are
concerned
about lost write coherency, then you ought to use jfs filesystems due
to its logging capability. Depending on the application, raw LVs may
have better performance, but that would depend on whatever driver
(i.e.,
the app) is being used. Essentially, the factors you should consider
are size of database needed (jfs filesystem has a 2Gb limit at AIX 3.2,
64Gb at 4.1, while raw LV has a max of 64Gb at either level),
performance (dependant on application), and coherency (probably better
with jfs, but then again, the application would decide this).
Keep in mind that jfs filesystems can now implement (automatically)
variable fragment sizes and data compression at 4.1.
These are a few factors to consider.
**************> QUESTION level 1 --> level 2 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN JAPAN
May I ask one more question?
I understand max size of a file is 2GB(both 3.2 and AIX 4.1) when we
are
using JFS. Then how large a file can we creat when we use raw devices?
Thanks in advance.
**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> ASGN: AUSVV AT WTSCPOK ======================== DATE:950906
TIME:1135
Received by Austin ITSC and assigned to AIXOPSYS.
Your question has been received, please wait for a reply.
**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> RESP: AIXOPSYS AT WTSCPOK ======================== DATE:950906
TIME:1548
Your question is being researched.
**************> ANSWER level 2 --> level 1 SPECIALIST <**************
====> THIS TEXT HAS BEEN ENTERED BY IBM IN USA
====> RESP: AIXOPSYS AT WTSCPOK ======================== DATE:950907
TIME:0850
Response:
Action: There is no "file" limitatation when dealing with a device.
You have a direct addresibility of 2gig, but with special programing
you can go to roughly 2 terabytes.
WWQA: ITEM: RS4000016661 ITEM: RS4000016661
Dated: 08/1995 Category: AIX6000
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