Are you running Sybase on Linux and on a bare metal server? Also, what is the data page size you have configured? Is it 2K, 4K, or 8K data page size? Please let me know so I can tell you which performance policy to use. Also, if you don't mind sharing with me the name of the company you're working for so we can work with SAP if needed.
I'm running a test installation of SAP Sybase ASE 15.7 on a VMWare virtualized Windows 2012 Server.
The database files are NOT within vmdks but are directly connected with 2 iSCSI Adapters.
(This is a configuration that works fine with all our production servers running maxDB)
From the SAP instruction manual i read that SAP works with 16k data page size.
That's how SAPinst configures the db during the install procedure.
From the course i visited last week i also recall 2 different I/O pools within the data cache, 16 k and 128 k.
so, i am a bit confused ;-)
The purpose of our performance policies is to match, as closely as possible, the default block size of the application using the volume. In the absence of a direct match, any evenly divisible multiple will work as long as some basic rules are followed:
The general rule is Nimble Block size <= OS's File allocation unit size (disk format option) <= Application's default I/O size.
For 16kB I/O's, a 16kB performance policy would work well provided the underlying OS's allocation unit size is also 16kB or larger. For the 128k pool, any block size should work as they're all factors of 128k. The trick is to use the largest block size on the Nimble side as you can get away with provided the general rule is followed. Once the block size is set, the other components of the perf policy, compression and caching, can be changed on the fly as needed.
Hope this helps!
> I'm running a test installation of SAP Sybase ASE 15.7 on a VMWare virtualized Windows 2012 Server.
Based on the above, the real question is, what NTFS allocation unit size was chosen with the disks were formatted. Default is 4k. In which case Nimble should also use a 4k performance policy, cache enabled, compression enabled for DB.
If you altered the NTFS allocation units to 8k or 16k, then again a Nimble policy that matches should be chosen/created.
The following article states that the default page size for the application is 4k, but it can be configured higher. SyBooks Online
Overall the rules mentioned by Rick Hellman should be followed.
Nimble block size <= File System Allocation Unit <= Application Page size.