On 11/14/2012 11:14 AM, Michel Jansens wrote: > Hi, > > I've ordered a new server with: > - 4x600GB Toshiba 10K SAS2 Disks > - 2x100GB OCZ DENEVA 2R SYNC eMLC SATA (no expander so I hope no > SAS/SATA problems). Specs: > http://www.oczenterprise.com/ssd-products/deneva-2-r-sata-6g-2.5-emlc.html > > I want to use the 2 OCZ SSDs as mirrored intent log devices, but as the > intent log needs quite a small amount of the disks (10GB?), I was > wondering if I can use the rest of the disks as L2ARC? > > I have a few questions about this: > > -Is 10GB enough for a log device?
A log device, essentially, only needs to hold a single transaction's-worth of small sync writes, so unless you write more than that, you'll be fine. In fact, DDRdrive's X1 is only 4GB and works just fine. > -Can I partition the disks (10GB + 90 GB) and use the unused (90GB) > space as L2ARC? Yes, you can. > -If I use the rest of the disks as L2ARC, do I have to mirror the L2ARC > or can I just add 2 partitions (eg: 2 x 90GB = 180GB) L2ARC doesn't have mirroring, it's always striped. > -If I used non mirrored L2ARC, Could something go wrong if one L2ARC > device failed (pool unavailable,lock in the kernel, panic,...)? No, an L2ARC only holds non-dirty data from the main storage pool for quick access, so if a read to an L2ARC device fails (due to it failing, being removed, or returning bad data), then the read is simply reissued to the main pool drives transparently (and fault-management kicks in to handle the problem with the L2ARC, such as taking it offline, etc.). Cheers, -- Saso _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
