On Nov 10, 2013, at 10:12 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote: > USB is not a storage protocol. USB devices often disconnect/reconnect > for no apparent reason. We see this frequently with the little vendor > USB disk drives (Seagate/WD) and also generic disk enclosures. USB is > not a proper protocol for md/RAID storage. You may have continual > problems with this setup. > > If the laptop has an eSATA port use eSATA. If not, drop in an eSATA > PCMCIA card. This should be much more reliable than USB for this > application. Actually, it's a good piece of advice. Now all I need is to figure out if I I can do this with the hardware I've got. However, I feel compelled to say that my USB drives (I have had several… 4 to be precise, now 5) have been incredibly reliable throughout all these years. No connection problems whatsoever, no flakiness/flapping of any kind. Very solid and reliable as for a home, midrange 7 years old laptop and three 7 years old drives. I've been using them for all sorts of things, from backups to torrents and storing virtual machine disk images, etc. Very reliable. The only concern I have is that performance sometimes may not be enough, but by and large it is not a problem for me and so I get by just fine. Installing an eSATA PCMCIA card is actually a great idea, and I almost falmpaced when I realized I could've probably resolved performance issues long time ago and the solution was in front of me all this time, but then again the problem was from a pressing character and so I have been really content most of the time with what I have. > >>> Also, I see little/no value in running a scheduled mdadm check on a >>> RAID1 array. Any problems with RAID1 will be due to one of the disks >>> beginning to fail in some mode, usually requiring sector relocation. >>> Most drives do this automatically until they run out of spare sectors, >>> at which point md will throw write errors. Monitoring SMART data and/or >>> running SMART self analysis on a schedule is much more effective here, >>> as you will become aware of a problem sooner, and have the opportunity >>> to correct it before it shows up in md. >> >> Bare with me, I know very little about how RAID works so I can sometimes make totally absurd statements. That being said, I intend to monitor SMART values and I'm wondering now why does it make sense to run check on other types of RAID? I assume 5/6/10 mostly? >> >> I'm also wondering if it is advised to run check with filesystem mounted and in use, or unmounted? > > Instead of using a connection method known to cause problems with > storage, and then attempting to mitigate such damage with array/fs > checks after the fact, why not simply avoid the problem in the first > place? Use eSATA, or build/buy a little NFS/Samba NAS filer. > As I said in my particular configuration it is a pretty solid connection. No experience with NAS filers here, but I'm definitely looking this option up as well (already googled it up and reading a description). What about filesystem state? Does it matter if a filesystem is mounted when check is run? Ivan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
