Hello, I am in the process of planning for a SQL 2005 64 bit install using ESX 3.5 and a new Dell EqualLogic SAN. I am trying to decide how I can best utilize snapshot functionality of the SAN but am hitting some roadblocks and was hoping I could get some insight here. I submitted a ticket with EqualLogic to see what they would recommend and here is their response:
With SQL databases you have a couple of options for giving you the capability to create an "application consistent" snapshot of your databases/log files. The best method would be to just place your SQL databases and log files on separate iscsi volumes and use the "storage direct" approach and connect to these from inside the guest OS (W2K3, etc) using the MS initiator and then installing the HIT kit with ASM in the guest so that you can take advantage of Microsoft's Volume Shadow Copy Services for taking an application consistent (quiesced) hardware snapshot of the DB and log volumes for SQL. This gives you the granularity of restoring the SQL databases directly and playing back logs as needed.
Another method is to use the newer ASM VMWare edition which will allow you to take a VM guest OS consistent snapshot of the vm itself on a datastore. This will allow you to restore the whole vm instead of just the SQL application. If the SQL database files reside inside the vmdk as well as the log files then this would take an application and OS consistent snapshot which is hardware based on the array just like the ASM from inside the guest OS. The main difference is that you do not have all the granularity and ability to restore down to specific databases.
ASM VE uses the SYNC driver which is a component of VMWare tools. The SYNC driver quiesces and holds incoming I/O and then flushes the file system's buffers to disk, thereby making the file system consistent.
Note: VMware does not support the SYNC driver on 64-bit guest operating systems and any operating
system other than Windows. As a result, ASM/VE will skip the VMware snapshot step for unsupported
guests. However, it will continue to take the PS Series array snapshot. In these cases, the snapshot will
have a crash-consistent file system. For more information regarding the SYNC Driver, refer to VMware's
Virtual Machine Backup Guide.
It looks like I should be looking at using the "storage direct" approach if I want to stick with 64 bit SQL but I really like the simplicity of keeping everything in vmdk files. So here are my questions:
1. If I use the storage direct approach do I have to be concerned about any other issues (besides not fully being able to use VMware snapshots)? I.E. I assume VMotion would still work fine, for example, but just wanted to check.
2. It surprises me that the SYNC driver does not support a 64 bit guest OS. Is there any buzz or hope that this will be supported in the next release of ESX? I could stand waiting 6 months if I knew it was coming.
3. Should I just consider using 32 bit w2k3 and 32 bit sql instead? the possible performance benefits and 64 bit are the driving factor for me there but it also seems that 64 bit can bring some extra challenges with esx so I wanted to get some thoughts on that also.
Thanks in advance for any help you can provide
Chad
