Ahmed Kamal wrote: > Thanks for all the opinions everyone, my current impression is: > > - I do need as much RAM as I can afford (16GB look good enough for me) > - SAS disks offers better iops & better MTBF than SATA. But Sata > offers enough performance for me (to saturate a gig link), and its > MTBF is around 100 years, which is I guess good enough for me too. If > I wrap 5 or 6 SATA disks in a raidz2 that should give me "enough" > protection and performance. It seems I will go with sata then for now. > I hope for all practical purposes the raidz2 array of say 6 sata > drives are "very well protected" for say the next 10 years! (If not > please tell me)
OK, so what the specs don't tell you is how MTBF changes over time. It is very common to see an MTBF quoted, but you will almost never see it described as a function of age. Rather, you will see something in the specs about expected service lifetime, and how the environment can decrease the service lifetime (read: decrease the MTBF over time more rapidly). I've not seen a consumer grade disk spec with 10 years of expected service life -- some are 5 years. In other words, as time goes by, you should plan to replace them. A more lengthy discussion of this, and why we measure field reliability in other ways, see: http://blogs.sun.com/relling/entry/using_mtbf_and_time_dependent > - This will mainly be used for NFS sharing. Everyone is saying it will > have "bad" performance. My question is, how "bad" is bad ? Is it worse > than a plain Linux server sharing NFS over 4 sata disks, using a > crappy 3ware raid card with caching disabled ? coz that's what I > currently have. Is it say worse that a Linux box sharing over soft raid ? > - If I will be using 6 sata disks in raidz2, I understand to improve > performance I can add a 15k SAS drive as a Zil device, is this correct > ? Is the zil device per pool. Do I loose any flexibility by using it ? > Does it become a SPOF say ? Typically how much percentage improvement > should I expect to get from such a zil device ? See the best practices guide: http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
