It's time for me to say something nice about ZFS for a change, becauseZFS can make the big RAID-5 problem significantly less of a problem for many people. ZFS offers twosignificant advantages:

• because it knows what parts of the array actually contain live data,it doesn't need to read all of the disks. Less data read means lesschance of an unrecoverable read error.

  (How much of an improvement this is depends on how full your poolsare; if you routinely run with very

Let's start by talking about drive failure modes andhow they're measured. Hard drives have both MTTF , the rateat which they fail completely, and UER , the rate at which they report an unreadable sector. Drive MTTFis expressed in hours, but drive UER is expressed as a function of howmuch data is read (technically as 'errors/bits read').

(Typical consumer drive drive UER is apparently 1 per 10 ¹⁴ bits read; 'enterprise' disks improve this to

The more I think about it, the more I think that there are a numberof conditions that need to hold in order for overlapping windowsto make sense (or at least to be attractive). I also think thatthese conditions are not necessarily all that prevalent, which maygo a long way towards explaining why tabs and maximized windows are so popular.

First, small displays lead to maximized windows (and thus tabs) becausethere isn't enough space to go around. This isn't just resolution,

One of the strange networking mysteries around here is that every sooften, one of our login servers will report that outgoing mail wasdelayed because it could not connect to the mail server's SMTP port.There's several things that make this puzzling:

• the connection is failing with 'host not reachable' errors, not'connection refused' or the like
• the mail server is up, running fine, and not loaded at all
• the login servers and the mail server are on the same subnet,although they are