On Wed, Sep 16, 2009 at 08:02:35PM +0300, Markus Kovero wrote: > It's possible to do 3-way (or more) mirrors too, so you may achieve better > redundancy than raidz2/3
I understand there's almost no additional performance penalty to raidz3 over raidz2 in terms of CPU load. Is that correct? So SSDs for ZIL/L2ARC don't bring that much when used with raidz2/raidz3, if I write a lot, at least, and don't access the cache very much, according to some recent posts on this list. How much drive space am I'm losing with mirrored pools versus raidz3? IIRC in RAID 10 it's only 10% over RAID 6, which is why I went for RAID 10 in my 14-drive SATA (WD RE4) setup. Let's assume I want to fill a 24-drive Supermicro chassis with 1 TByte WD Caviar Black or 2 TByte RE4 drives, and use 4x X25-M 80 GByte 2nd gen Intel consumer drives, mirrored, each pair as ZIL/L2ARC for the 24 SATA drives behind them. Let's assume CPU is not an issue, with dual-socket Nehalems and 24 GByte RAM or more. There are applications packaged in Solaris containers running on the same box, however. Let's say the workload is mostly multiple streams (hundreds to thousands simultaneously, some continuous, some bursty) each writing data to the storage system. However, some few clients will be using database-like queries to read, potentially on the entire data store. With above workload, is raidz2/raid3 right out, and will I need mirrored pools? How would you lay out the pools for above workload, assuming 24 SATA drives/chassis (24-48 TBytes raw storage), and 80 GByte SSD each for ZIL/L2ARC (is that too little? Would 160 GByte work better?) Thanks lots. -- Eugen* Leitl <a href="http://leitl.org";>leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
