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To: Thomas Mercer-Hursh who wrote (31565)	9/13/2000 8:49:54 PM
From: Thomas Mercer-Hursh	Read Replies (1) \| Respond to of 54805

Well, to answer my own question ... none of the above; it's RAID 4, which I haven't run into for a while. So, the question then becomes whether one can truly trust the NVRAM cache. What they say sounds good, but then vendors have been telling us for years that their write caches were completely safe and it was a lie. Given the sophistication of the rest of the product, I will assume for the present that it is safe and that this masks the potential performance penalty for writes, but were I buying one, it is something I would want to look into more deeply unless I found a source I could believe. So, let's turn this upside down and say that it seems to be a potential advantage of NTAP that it seems to provide RAID 4 protection, but unlike virtually every server-attached RAID controller, it can be safely used with the cache enabled in a RAID 4 or 5 mode.

To: Thomas Mercer-Hursh who wrote (31565)	9/14/2000 8:15:04 AM
From: DownSouth	Read Replies (1) \| Respond to of 54805

Thomas, NTAP uses RAID 4, which is a dedicated parity drive in each array. This gives the flexibility of adding additional drives to an array "on the fly", with no need to backup and restore or even "down" the array. NTAP can use RAID 4 because of they way WAFL manages free blocks and head movement. The disadvantages that other file systems have with RAID 4 are overcome by WAFL. Also, NTAP's use of non-volatile RAM (NVRAM) is so reliable that cached writes are always completed, even in the case of a catastrophic failure. That is why ORACLE and other RDBMS vendors support NTAP's NFS mounts as RDBMS data volumes. NTAP's are the only NFS mounts supported by these vendors.