i/o read/write caching

MattBoB · Thu Nov 08, 2007 11:41 am

I am using licensed version of starwind professional and was wondering about the RAM caching. Is this enabled by default? Do I have to select the "Use file system buffering" option to enable it?

Thu Nov 08, 2007 9:19 pm

Yes, you need to check this box to enable extensive RAM caching. However it's not recommended ATM as our latest test show it does provide benefits only to a very small set of the software. So for now (until version 3.5.1) just keep the things AS IS.

MattBoB wrote:I am using licensed version of starwind professional and was wondering about the RAM caching. Is this enabled by default? Do I have to select the "Use file system buffering" option to enable it?

MattBoB · Fri Nov 09, 2007 11:54 am

OK, thanks for the prompt reply.

Could I put in a request for future versions to have an option to allow read only RAM caching aswell. I am nervouse of using RAM to cache writes as this could result in data corruption should the server starwind is running on crash for any reason. Having a UPS only covers power outages. My experience of starwind so far is its rock solid stable but still better to safe than sorry in this game!

Fri Nov 09, 2007 12:10 pm

You're not the only one complaining about this! So we'll move away from Cache Manager owned buffers to own caching in the next versions. With "write-thru", "write-back" and "read-ahead" caching only.

MattBoB wrote:OK, thanks for the prompt reply.

Could I put in a request for future versions to have an option to allow read only RAM caching aswell. I am nervouse of using RAM to cache writes as this could result in data corruption should the server starwind is running on crash for any reason. Having a UPS only covers power outages. My experience of starwind so far is its rock solid stable but still better to safe than sorry in this game!

MattBoB · Wed Dec 12, 2007 10:44 am

I notice verwsion 3.5.1 is now available, but no mention of any changes to caching. Are there any? Should I consider turning it on now?

Wed Dec 12, 2007 2:30 pm

Hi. We planned to include this feature in 3.5.1. But it hasn't been finished.
We are still working on it.

MattBoB · Wed Mar 05, 2008 2:17 pm

Another new version 3.5.3 - any update to this issue in this version?

Wed Mar 05, 2008 2:34 pm

Unfortunately no.
Still working on it.

BartHermans · Tue Apr 15, 2008 3:28 pm

Hello Anton.

We're planning to test StarWind in our labo environment. So this forum gives us already an idea what to check for. Even before reading all this information, we have doubts about the (write) caching mechanism.

Can you tell us what will happen to the data or volume if the M$ system (iSCSI target server) gives an unpredicted blue screen ?
Thats the same problem as with a system power failure.
HP servers are having some battery backup write cache on RAID controllers, and thats for a good reason.

Can we avoid this problem in any other way ?

Greatings from Belgium.
Bart & Peter.

Wed Apr 16, 2008 12:28 pm

If machine will BSOD all data stored in RAM (and not commited to the hard disk) will be lost... That's why we've turned OFF system caching for now and working on reliable private cache mechanism. Unfortunately whole OS with bunch of "alien" software installed is very much different from bugfree RAID firmware. And it will be RDS team to blame if gigabytes of data will be lost. So basically you're 200% - solution is not reliable AS IS. Unless you have dedicated IP SAN server with UPS and NO other software running. But in this case it's wiser to get Linux-based cheap IP SAN appliance.

BartHermans wrote:Hello Anton.

We're planning to test StarWind in our labo environment. So this forum gives us already an idea what to check for. Even before reading all this information, we have doubts about the (write) caching mechanism.

Can you tell us what will happen to the data or volume if the M$ system (iSCSI target server) gives an unpredicted blue screen ?
Thats the same problem as with a system power failure.
HP servers are having some battery backup write cache on RAID controllers, and thats for a good reason.

Can we avoid this problem in any other way ?

Greatings from Belgium.
Bart & Peter.

BartHermans · Wed Apr 16, 2008 4:11 pm

Anton,

At this moment we use one HP EVA4000 storage in conjuction with HP Blade VMware ESX servers. We want to offload and move some data to another storage tier using the same benefits of a FC SAN. Furthermore we are interested to use the replication possibilities. Your product has the capabilities to do so. As far as we have tested StarWind, the product looks promising...
If you say : 'That's why we've turned OFF system caching for now...' implicates this that write (read?) caching can be turned off in the latest version ? That's not yet clear to us.
Our datacenter is covered by UPS and no other software will be running on the IP SAN server. We're thinking about connecting the IP SAN server to the HP EVA4000 using a FC HBA and cheaper DAS storage for replication purposes.

Regards.

Wed Apr 16, 2008 7:11 pm

In the latest build we don't allow Windows to do write buffering (well, there's a secret switch to turn it optionally ON but I'd keep this info private). So I think you should be fine with this.

BartHermans wrote:Anton,

At this moment we use one HP EVA4000 storage in conjuction with HP Blade VMware ESX servers. We want to offload and move some data to another storage tier using the same benefits of a FC SAN. Furthermore we are interested to use the replication possibilities. Your product has the capabilities to do so. As far as we have tested StarWind, the product looks promising...
If you say : 'That's why we've turned OFF system caching for now...' implicates this that write (read?) caching can be turned off in the latest version ? That's not yet clear to us.
Our datacenter is covered by UPS and no other software will be running on the IP SAN server. We're thinking about connecting the IP SAN server to the HP EVA4000 using a FC HBA and cheaper DAS storage for replication purposes.

Regards.

BartHermans · Thu Apr 17, 2008 6:55 pm

Anton, thanks for the quick replies.
We've installed the trial version on a server with 2x RAID5 1.4 TB volume.
3 NIC's are connected to a dedicated GB switch, a fourth is connected to the LAN for domain purposes. We had some difficulties with a iSCSI initiator on a Win2000 server, but W2K is not the platform we use, so we dropped the problem and installed an initiator on a W2K3 server. Works like a charm. We've seen on the target server that we can dedicate a NIC to an image (in our case we had 3 GB NIC's) and that will perform quite well. We're going to drop big SQL backups on the target server to test the speed. After those performance tests we're going to put a mirror RAID1 (on another target server) in test. We'll give you feedback about the tests.

Our boss is waiting for some test results and want a couple of other technical propositions (Ex.: New or extra HP EVA, lower cost storage, iSCSI or Fibre solution etc...). So he can better decide what to buy for the next 3 or 4 years. Even when the product looks great and robust, he's concerned about support or future support for the application.
I saw the big list of all the customers you have. Do you have a reference in Belgium or the Netherlands for the StarWind software ?

I've found the 'starwind_licensing_msrp_price_list.pdf' and red that we can buy support or 3 years Annual Software Maintenance and bundles of five (5) or ten (10) pre-paid incidents. Once we have decided what our solution will look like (and StarWind is in the picture), we'll contact you for more information about the pre-paid incidents and the annual software maintenance.

Thanks,
Bart.

Fri Apr 18, 2008 2:27 pm

1) Sure! Please keep us updated about your progress.

2) I'll bring one of our NL reseller into conversation. Please drop me an e-mail to support@rocketdivision.com referencing you're you

3) Per-incident scheme was dropped. Now we don't keep track on number of support requests. We'll have to fix this, thanks a lot for pointing.

Thank you!

BartHermans wrote:Anton, thanks for the quick replies.
We've installed the trial version on a server with 2x RAID5 1.4 TB volume.
3 NIC's are connected to a dedicated GB switch, a fourth is connected to the LAN for domain purposes. We had some difficulties with a iSCSI initiator on a Win2000 server, but W2K is not the platform we use, so we dropped the problem and installed an initiator on a W2K3 server. Works like a charm. We've seen on the target server that we can dedicate a NIC to an image (in our case we had 3 GB NIC's) and that will perform quite well. We're going to drop big SQL backups on the target server to test the speed. After those performance tests we're going to put a mirror RAID1 (on another target server) in test. We'll give you feedback about the tests.

Our boss is waiting for some test results and want a couple of other technical propositions (Ex.: New or extra HP EVA, lower cost storage, iSCSI or Fibre solution etc...). So he can better decide what to buy for the next 3 or 4 years. Even when the product looks great and robust, he's concerned about support or future support for the application.
I saw the big list of all the customers you have. Do you have a reference in Belgium or the Netherlands for the StarWind software ?

I've found the 'starwind_licensing_msrp_price_list.pdf' and red that we can buy support or 3 years Annual Software Maintenance and bundles of five (5) or ten (10) pre-paid incidents. Once we have decided what our solution will look like (and StarWind is in the picture), we'll contact you for more information about the pre-paid incidents and the annual software maintenance.

Thanks,
Bart.

BartHermans · Thu Apr 24, 2008 7:45 am

Anton,

We've done the tweaking of the TCP stack as you described for a better network performance. We've done some measuring : a 1GB file copy to a normal share on the StarWind server and a 1GB file copy to an ISCSI disk (image file) on the StarWind server. The file copy to the share is twice as fast compared to the iSCSI copy. The Gbit NIC is going to 45% while copying to the share and 20% using the iSCSI copy.

The iPerf utililty gives us a speed between 800 and 900 Mbits/sec.

Do you have any remarks about our measurments ? Are they normal ?
Today we're going to put the first StarWind Server in our "acceptation labo" to be used with ESX 3.5

Regards.
Bart