On 20 February 2012 03:04, Al Thompson <althompson58(a)gmail.com> wrote: There's an impact but less than most people expect to see. If you really insist, you need to have a good (at least RAID-1 supporting) card but you must avoid any fakeraid implementations (where the real work is still done by CPU but it is not that easy to migrate, I haven't used one for a decade but they're still around - the first ever SATA interface card I got had a fakeraid implementation). Mirroring via mdadm is usually good enough. If you want to try, just plug a 2nd disk and build an array, it's always possible to (carefully) dismantle the array later and go back to single disks. Day job mainly involves around high performance OLTP databases, we never use software raid since the servers we use always have decent SAS interfaces with good RAID support. Use of software RAID rarely comes up but sometimes it does and we lose about 1-2% performance overall.

On 19 February 2012 21:25, Michelle Konzack <linux4michelle(a)tamay-dogan.net> wrote: I'd love to see a FAKE SAS drive. Only 4 years ago, 4TB SAS http://www.theregister.co.uk/2008/04/08/seagate_1tb_sas_drives/ 2 years ago, 2TB SAS: http://www.seagate.com/ww/v/index.jsp?locale=en-US&name=constellation-e… A year and a bit ago, 3TB SAS: http://www.storagenewsletter.com/news/disk/hitachi-gst-3tb-ultrastar-7k3000 Also the physical properties of the disks don't matter much apart from the RPM hence the seek time and a bit with the number of the platters (not as much as the RPM). The rest are identical between SAS and SATA apart from the interface. The enterprise-level disks also tend to come from better-end of the quality testing, that makes a difference to the failure rate thus they also cost more. If you want real performance, go for 15k SAS drives but they will do damage to your bank account but will have very short seek times but the performance increase is usually not that significant. Here's an ancient but a good read: http://www.tomshardware.com/reviews/sas-hard-drives,1702.html On the other hand, the idea of just having SAS having a higher performance is a fiction. SAS-3 gives you 6Gbit/s bandwidth. SATA-3 gives you 6Gbit/s bandwidth. SAS has better error protection etc. and just because it's more enterprise, better quality of disks but it doesn't mean it is just faster. Thanks to SAS disks supporting SCSI protocol, you can have multipathing etc. but those don't apply to desktops, mainly server-side business.You used to get additional performance on SCSI ends (serial or parallel) by having queueing implemented but new SATA drives have similar technologies too. Compare the details for yourself: http://en.wikipedia.org/wiki/Serial_attached_SCSI http://en.wikipedia.org/wiki/Serial_ATA All said, having SAS drives & cards is not a bad idea. You will be using better tested hardware and will have lower failure rates. If this is important, paying for the extra amount is worth it. Also using good SAS interface with loads of memory and on-board battery will make sure that at a failure your data will be written to the disk. On the other hand you will not get a lot of these on consumer-grade hardware, you will need a noisy server but almost all servers (HP/Dell/IBM/Fujitsu etc.) will supply you with a somewhat decent SAS interface and, if you have serious data requirements, external enclosure with no performance penalties. Just keep the server away from your recording studio!