On Wed, Mar 16, 2005 at 07:29:50PM -0600, Rushforth, Tim wrote: [DIRMC] > What in 5.3 warrants new consideration?
Probably the fact that sequential volumes are written to in blocks of at least 256 KB, even when the data is only 1500 bytes. This can cause a lot of overhead, and the effective capacity of sequential volumes could be reduced by a factor of 60 or more. Note that a great number of factors influence the above statement. On the one end, it could cause a perfectly OK setup under 5.2 to be unusable under 5.3. On the opposite end, you might notice no adverse effects and even experience a performance improvement. In the case of FILE storagepools used as a DIRMC destination, you might find yourself in the first scenario (works under <= 5.2, doesn't work under 5.3). You might be able to alleviate this by adjusting the TXNGROUPMAX server setting and the TXNBYTELIMIT client setting. Unfortunately, this doesn't affect data that's already in a storage pool. And unfortunately again, storagepools used as DIRMC destination often have quite generous retention settings, as per the documentation and general recommendation. Part of the reason that these retention settings could be generous was that directories were so small that it wouldn't matter a lot. With the new handling of sequential volumes, it does start to matter (and sometimes a lot). -- Jurjen Oskam