Christopher Chan wrote: > William Warren wrote: > > I'm not a fan of RAID 5 at all since it can only tolerate one failure at > > all. Go with raid 10 or something like that which is able to handle > > more than one failure. Intermittent, uncorrectable sector failures > > during rebuilds are becoming an increasing problem with today's drives. > > > > Is that raid10 or raid 1+0 or raid 0+1? :D > > At least for the latter two, their handling more than one failure > depends on which disks blow. Not sure how the raid10 module > handles things. Whoever implements RAID10 will want the RAID1+0 which is a stripe set of mirrors, rather then the RAID0+1 which is a mirror of stripe sets. The problem being two fold, 1) in a RAID0+1 a single drive failure on either side of the mirror will put the whole array into total failure jeopardy, a failure on both sides is a total loss, 2) the pathway for simultaneous operations is cut down from (say X is an even number of disks) X reads, X/2 writes, to 2 reads, 1 write. On a RAID5/6 array you are limited to a pathway of 1 read and 1 write at a time and all writes must write across the entire stripe, so if you do choose RAID5/6 then it is highly recommended to use a hardware RAID controller with a BBU write-back and read-ahead cache which can minimize the impact of this by caching a whole stripe set to write at once and to have a stripe set of reads waiting for io requests. For database log files and other applications that do a lot of random io it is recommended to use fast RPM drives in a RAID10 which has the multiple pathways for reads and writes which will maximize the total number of random IOPS (ios per second). Typically most vendors recommend a two-prong approach, keep the database data files on a RAID5/RAID6 type array and keep the log files on a RAID10 array. -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.