RAID-1 vs. RAID-5

BROWSE BY TAG Primary Storage or Storage Hardware,   RAID,   VIEW ALL TAGS

Digg This!     StumbleUpon     Del.icio.us

RELATED CONTENT RAID Pivot3 and Seanodes increase performance, scalability of iSCSI storage products Fujitsu adds DX60 and DX80 midrange disk arrays to Eternus line Storage Decisions Chicago 2009 Session Downloads MAID technology remains underutilized The state of MAID in data centers MAID product roundup The evolution of RAID data protection RAID changes its stripes, but not its value Post-RAID products Faster disk drive rebuilds: Hot Spots RAID Research

RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary disk cache  (SearchStorage.com) disk duplexing  (SearchStorage.com) disk striping  (SearchStorage.com) double-parity RAID  (SearchStorage.com) hard disk  (SearchStorage.com) hard disk drive  (SearchStorage.com) parity  (SearchStorage.com) RAID  (SearchStorage.com) storage medium  (SearchStorage.com)

RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary

I don't recommend using RAID-5 for any sort of write-intensive work at all. RAID-5 performance is notoriously slow for writes, especially small writes, because of the CPU overhead that each write requires. The overhead is worse if the RAID-5 is software-based. Hardware-based RAID-5 is better, but still not as fast as RAID-1. Of course, RAID-1 requires a great deal of extra disk space (double the usable space you need), so you pay for each approach in different ways.

Can you put the OS on RAID-5? Yes, you can, but I believe you'll find that the system's performance will suffer.

Can you divide a RAIDed slice into multiple partitions? You may be able to, depending on the hardware and software you use, but I think you'd be better served by having two or more separate RAID slices, and assigning each to a separate file system.

Does RAID-5 take a long time to rebuild? Short answer: YES. Long answer: It depends on how large the RAID-5 slice is, how many disks it is striped across, the I/O speed of the disks involved, the CPU speed of the system(s) involved, how much other work is underway and lots of other factors. I have seen large, poorly configured RAID-5 slices take days to rebuild.

The optimal configuration for RAID-5 is to have data spread across four to six disks. Fewer than that is not worth it: You may as well consider RAID-1. More than that invites trouble by increasing the likelihood of multiple disk failures. And, more disks require more time to rebuild.