Eric Schrock wrote:
On Tue, Jun 20, 2006 at 11:17:42AM -0700, Jonathan Adams wrote:
On Tue, Jun 20, 2006 at 09:32:58AM -0700, Richard Elling wrote:
Flash is (can be) a bit more sophisticated. The problem is that they
have a limited write endurance -- typically spec'ed at 100k writes to
any single bit. The good flash drives use block relocation, spares, and
write spreading to avoid write hot spots. For many file systems, the
place to worry is the block(s) containing your metadata. ZFS inherently
spreads and mirrors its metadata, so it should be more appropriate for
flash devices than FAT or UFS.
What about the UberBlock? It's written each time a transaction group
commits.
Yes, but this is only written once every 5 seconds, and we store to 256
different locations in a ring buffer. So you have (256*100000*5)
seconds, or about 100 years.
100k writes is the de-facto minimum. In looking at some SSD (yes, they
are marketing them as solid state disks) drives with IDE or SATA interfaces,
at least one vendor specs 5,000,000 writes, sizes up to 128 GBytes. It
will be a while before these are really inexpensive, though.
-- richard
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