> If you want Dedup to perform well, you *absolutely* must have a L2ARC > device which can hold the *entire* Dedup Table. Remember, the size of > the DDT is not dependent on the size of your data pool, but in the > number of zfs slabs which are contained in that pool (slab = record, > for > this purpose). Thus, 12TB worth of DVD iso images (record size about > 128k) will consume 256 times less DDT space as will 12TB filled with > text configuration files (average record size < 512b). > > And, I doubt 8GB for ARC is sufficient, either, for a DDT consuming > over 100GB of space.
The test was run on a test machine with a small (160GB IIRC) root disk, 7x2TB disk in RAIDz2 plus 2 80GB Intel X-25M SSD gen 2. The box has 8GB RAM/ARC, and was configured with two mirrored 4GB partitions on the SSD for SLOG and the rest for L2ARC. The data stored on the system, was Bacula output, meaning more or less streaming to large files. Recordsize was set to 128kB. The initial performance was good, but after filling up about 2TB, performance was down to a 25% of the initial, and AFAICS with only 2TB, even 8GB ARC should suffice for the DDT. Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 97542685 r...@karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
