Limits on RamDisk w/ SQL?

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drosenberger
Posts: 1
Joined: Tue Nov 07, 2017 4:14 pm

Limits on RamDisk w/ SQL?

Post by drosenberger » Tue Nov 07, 2017 4:18 pm

We are currently using your Primo Ramdisk Server Edition (v5.7.0) on the following machine..

- Role: MS SQL 2016 Standard with SP1
- Total server ram 384gb DDR4 2400
- CPU Intel Xeon E5-2697A v4 16core

We have been encountering an issue with an instance of SQL server running on the box that…

- Uses its “TempDB” stored on a Ramdisk made by your product
- In that the entire instance gets “stuck” on a single 8k page of TempDB
- And in turn brings the entire instance to a crawl / halt for seconds (minutes at times)
- And in turn causes issues w/ our platform.

We’ve been using PrimoRamdisk for some time now w/ out issue or occurrence of this, and we are wondering…

- Is there some type of “limit” to the iOPS that can go through your software’s ramdisk?
- Is there a windows perfmon counter we can watch to see if this is the case?
- Are there any special settings or “tricks” that you can pass along for best configuring your product to work w/ MS SQL?
o Any changes we should make to MS SQL server itself to work with your product better?
o I’ve attached a zip file containing the disk descriptor for this server


- Could this be caused by CPU pressure?
o If the server was at 100% CPU, is it possible it’s not going to be able to work with your RAMDISK correctly?

Any help would be greatly appreciated!
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support
Posts: 2221
Joined: Sun Dec 21, 2008 2:42 am

Re: Limits on RamDisk w/ SQL?

Post by support » Tue Nov 14, 2017 4:27 am

drosenberger wrote:Is there some type of “limit” to the iOPS that can go through your software’s ramdisk?
No.
drosenberger wrote:Are there any special settings or “tricks” that you can pass along for best configuring your product to work w/ MS SQL?o Any changes we should make to MS SQL server itself to work with your product better?
I see that an image file is associated to the ramdisk and the "timing save" option is enabled. This might cause lag especially when CPU is at 100% usage because the ramdisk has to write dirty data to the associated image file every specified intervals.
Another thing you may try is to change the ramdisk type from DirectIO to SCSI, if you still have the problem. A SCSI ramdisk is slower than a DirectIO ramdisk, but it acts like a real disk.
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Girawuth
Posts: 1
Joined: Mon Nov 19, 2018 6:45 am

Re: Limits on RamDisk w/ SQL?

Post by Girawuth » Mon Nov 19, 2018 7:04 am

I'm also looking for information about this as well.

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