Hello Balanand, There is no parameter per se in Solaris 8 & 9 (the ones that I use). But there are several parameters in Solaris that relate to # of bytes which can be read in a single I/O call.
The maxphys kernel parameter limits I/O in the SCSI layer within the kernel. Default is 128k. We are using Solaris Volume manager; within the SVM layer there is a md_maxphys kernel module parameter that limits within that subsystem. If not specified then it defaults to maxphys. There is a corresponding parameter if you are using Veritas volume manager, but I am not sure what it is vxd_maxphys or something. Can someone else confirm ? SD (scsi) devices used the cd module and they describe a sd_max_xfer_size parameter that limits max I/O size within that type of device. Default is 1MB SSD (fibre channel scsi) devices used the cd module and they describe a ssd_max_xfer_size parameter that limits max I/O size within that type of device. Default is 1MB Hope this helps.. Jason Harris -----Original Message----- From: PINNI, BALANAND (SBCSI) [mailto:[EMAIL PROTECTED] Sent: Thursday, February 05, 2004 4:45 PM To: [EMAIL PROTECTED] Subject: Re: MAX_IO_SIZE on AIX Can any body tell me how to find out the MAX_IO_SIZE in solaris? =============== Answer: =============== The "maxphys" kernel parameter limits the max. I/O size in the SCSI layer. Default is 128k. The "vol_maxio" kernel parameter limits the max. I/O size in the VxVM layer (if installed). Default is 256k. The "md_maxphys" kernel parameter limits the max. I/O size in the DiskSuite/SVM layer (if installed). Default is equal to maxphys. The "sd_max_xfer_size" module parameter limits the max. I/O size in the SD module (if installed). Default is 1 Mb. The " sd_max_xfer_size" module parameter limits the max. I/O size in the SSD module (if installed). Default is 1 Mb. There is a good doc on I/O size limits in the following Technote : -- 08-02-2002 Set the default max. I/O size in Veritas to match/exceed the max. I/O size that will be used. in /etc/system, place set maxphys=1048576 set vxio:vol_maxio=2048 * to allow 1MB I/Os. vol_maxio is in Veritas units i.e. disk sectors of 512 bytes. maxphys is in bytes. We used to have exactly the same issue with DiskSuite, BTW, and needed to set md:md_maxphys in /etc/system. However, I understand DiskSuite was modified to check the kernel maxphys value and use that to override md_maxphys if it was larger. It is convenient to only have to turn one knob. -----Original Message----- From: Russell Brooks [mailto:[EMAIL PROTECTED] Sent: Thursday, February 05, 2004 6:15 PM To: [EMAIL PROTECTED] Subject: MAX_IO_SIZE on AIX Hi, We using ADSM and RMAN to backup our databases. I've run across a tuning recommendation dependent on max_io_size. AIX does not appear to have this parameter, though it has been suggested that maxpgahead may provide similar information. Does anyone have information on correlation of these two parameters? Any insights from people who've been down this path would be appreciated. Thanks, Russ Brooks [EMAIL PROTECTED]
