RE: Max IO size - File System vs Raw

From: Christopher Spence <cspence_at_FuelSpot.com>
Date: Thu, 06 Sep 2001 06:59:35 -0700
Message-ID: <F001.0038525F.20010906065101@fatcity.com>

A lot of file system's have a max io of much lower than raw. In the earlier Solaris's it was 64K, but as you see, it is now seems to be 256k. Under NT is 128k without using raw.

To truly take advantage of MULTIBLOCK_READ_COUNT you need to use RAW file system. HP_UX I believe can do as high as 1Mb for this.

"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."

Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275

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-----Original Message-----
Sent: Thursday, September 06, 2001 9:11 AM To: Multiple recipients of list ORACLE-L

Anyone know of any restrictions on the max physical IO (under Solaris8) that is imposed by file systems? To illustrate -

Using a tablespace on a raw device under veritas vol mgr
- maxphys is 512k

vxio:vol_maxio is 512k
db block size is 8k
db multi read is 64 and as expected, a level 8, 10046 trace shows me that I can get 512k max io...so far, so good

If I repeat the exercise after putting a file system (vxfs or ufs) on this device, then the best I can get is 256k.

Any Solaris internal people out there ?

Cheers
Connor

Connor McDonald
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Received on Thu Sep 06 2001 - 08:59:35 CDT