Hi David,
The default for VSP is to allow the cache file to grow to 30GB. For nearly all situations this is totally impractical. If you must use VSP then your best option is to "tune" it and set the default initial size, and the maximum allowed size. An initial size of 500MB and a maximum of 1000MB is usually enough. Only rarely will the maximum need to be higher. As ever, Symantec/Veritas have applied a one size fits all approach that doesn't actually suit all situations - in fact, I hazard a guess that you don't have many long time production servers with that much disk space free on any volume, so you actually risk interrupting (corrupting?) business applications by leaving the default settings in place.
N.B. The VSP drive exclusion list actually means two things:
1) Do not use VSP to secure the drive(s) listed - and....
2) Do not store a VSP cache file on the listed volumes.
.e.g If I enter C in the VSP exclusion list, then VSP will not be used to secure the C drive, and a VSP cache file will not be stored on the C drive when securing any other drive. My recommendation is to always specify C in the exclusion list, as this speeds up backups. I have never seen any difference between a backup that uses VSP to secure the C drive and a backup that has it excluded. The same busy files are always reported whether VSP is used or not, thus there's no need.
Another good reason to exclude the C drive from VSP is that VSP waits for a quiet moment on disks before it can create its cache file, and this again delays backups. Windows is very chatty on the C: drive, and in quite a few situations VSP busy wait timeout expires anyway, and thus a cache file doesn't get created (on another volume). Also, if you don't specify C in the exclusion list, then it is possible that the C drive gets used to cache writes for another volume - thus you will effectively be slowing down your system drive with many writes for another volume. This is not good for critical applications.
If there is a specific reason for using VSP, then the best situation is to have a completely separate drive to be used purely for holding the temporary cache file, but you will also need to exclude this particular drive from backups, and ensure that you do not use the "spare" drive for any other purposes.
If you use any anit-virus products then I strongly recommend that you exclude:
for v5.x: Z:\*.vsp
for v6.0: Z:\_vspcache
(please double check these file and folder specifications - I think they're right.)
...from the anti-virus scanning, as A/V products lock onto the cache files and wait for them to close, but VSP can't close the file because A/V has a lock, and thus after a deadlock timeout, VSP fails, and the fcache file gets left behind. This behaviour can also happen when VSP runs of of disk space whilst it allocates up to 30GB of disk space.
In summary:
VSP slows backups down (extra overhead and processing).
VSP causes unneccessary delays (initial wait for quiesce and waits for busy/locked files).
VSP causes excessive I/O (at least double the amount of disk writes, i.e. not only the natural write, but also a copy write to the cache file).
My $0.02.
Normally there's no need at all to use VSP, VSS or OTM. It's simply there because Symantec/Veritas choose to install and enable it by default. I have never seen any benefit from using VSP - only problems. The early version of v5.1 and v6.0 are notorious for isses with Windows O/S - and only the later MP packs, with a few key MS updates managed to get VSP to be fairly stable.
My recommended settings are:
a) Always exclude C.
b) Always set maximum initial size to 500MB (don't use the %age disk space option)
c) Always set the maximum size to 1000MB (i.e. 1GB).
d) Reduce the busy file wait from default 300 seconds to 30 seconds.
e) Set this for all Windows clients running v5.x and above.
I've had great success applying these settings at one site for all of over 80 different Windows clients (2000, 2003, Domino, Exchange, File/Print servers, SQL servers, proxy servers, web servers, FTP servers, monitoring servers, etc...). Only two clients (one of them a RIS server) actually required a larger maximum cache size of 3GB.
If you still have issues on any particular client, then try as David Parker described and completely disable VSP for the client in quiestion by using the client attributes properties on the master server.
Regards,
Dave.
