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<blockquote data-quote="auteur" data-source="post: 1057682207" data-attributes="member: 16170"><p>υπαρχει καποιος που να εχει δοκιμασει το FlexRAID ή SnapRAID + Stablebit Drivepool + Stablebit Scanner να μας πει εντυπωσεις;</p><p></p><p>διαβαζω για ενα σημαντικο θεμα που εχω αντιμετωπισει και δεν γνωριζα τι ηταν..</p><p>καποιες φορες σε αρχεία βιντεο ή σε FLAC/mp3 υπαρχουν καποια glitch (μάλλον απο bit rot..)</p><p></p><p>απο ότι διαβάζω αυτά διορθώνονται ΜΟΝΟ με το SnapRAID.. </p><p></p><p>αν ισχύει κατι τέτοιο, νομίζω ειναι μεγάλο θέμα.. </p><p>ειδικά για οσους αφιερώνουν αρκετές ώρες για να ψηφιοποιήσουν τις ταινιες τους και τα cd τους..</p><p></p><p>[SPOILER]As I understand it (I've read a lot of stuff on the flexraid forums and others before deciding on snapraid) Flexraid doesn't verify checksums when you update the parity, which means if you get silent errors and you don't check for them and fix them before updating parity, they could propagate into parity, making them impossible to fix... could have changed the last 2 years of course, but I haven't found anything solid to support that...</p><p></p><p>Flexraid doesn't verify checksums when you update the parity, which means if you get silent errors and you don't check for them and fix them before updating parity, they could propagate into parity, making them impossible to fix...</p><p></p><p>In the case of Snapraid it's simple...</p><p>when you scrub your array, it checks files (more accurately blocks) agains parity and it reports missing files, changed files and bit rot... etc... blocks that have bit rot will be marked as bad..</p><p>I myself had bit rot, it got detected by the scrub command and marked as bad... then I fixed it in a few seconds with the fix -E command...</p><p></p><p>Of course to make sure you don't have bit rot (or other degradation of your HDD) you have to regularly run the scrubs command (same with flexraid, there are also other snapshot realtime hybrids that do something like scrub on the fly, HW raid also does something similar)</p><p>The way snapraid or flexraid works, is that it calulates parity based on the data of the other drives... (very complicated)</p><p></p><p>this is where the difference between flexraid and snapraid comes in... </p><p></p><p>if you don't run scrub or flexraids couterpart regularly, you could have bit rot and when you sync your array, flexraid might calculate new data based on the files that have bitrot... so when you run validate (flexraids version of scrub) it will still detect bit rot, but "Verify" will report no problems, making it impossible to fix it...</p><p>On snapraid however when you sync your array it will check the files it uses to calculate parity for the new files against old parity first and if it encounters problems (like bit rot) it will stop and mark that block as bad. You can then run fix -E and it will fix the bit rot and you can resume the sync...</p><p>you so you know, this is a big oversimplification to how snapraid/flexraid works, it's a bit more complicated, but this is just so you understand what happens...</p><p></p><p>I myself did not get snapraid (or any redundancy for that matter) because I was afraid to lose drives, because that is very rare in my experience.... But I did get bitrot a bunch of times, resulting in glitches in videofiles, which is totally annoying, since there is no way to check against that, unles you watch the whole video... snapraid gives me a way to do exactly that and also gives me a way to fix it.. Of course having to option to recover whole drives is awesome as well, if it ever comes to that..</p><p></p><p>this is btw also the reason a simple backup on anither drive doesn't help much... yes you can see that one file if different than the backup file, but you can't know if the backup file or the original one has bit rot, unless you watch it... (without using any software that also does checksums etc)</p><p>[/SPOILER]</p></blockquote><p></p>
[QUOTE="auteur, post: 1057682207, member: 16170"] υπαρχει καποιος που να εχει δοκιμασει το FlexRAID ή SnapRAID + Stablebit Drivepool + Stablebit Scanner να μας πει εντυπωσεις; διαβαζω για ενα σημαντικο θεμα που εχω αντιμετωπισει και δεν γνωριζα τι ηταν.. καποιες φορες σε αρχεία βιντεο ή σε FLAC/mp3 υπαρχουν καποια glitch (μάλλον απο bit rot..) απο ότι διαβάζω αυτά διορθώνονται ΜΟΝΟ με το SnapRAID.. αν ισχύει κατι τέτοιο, νομίζω ειναι μεγάλο θέμα.. ειδικά για οσους αφιερώνουν αρκετές ώρες για να ψηφιοποιήσουν τις ταινιες τους και τα cd τους.. [SPOILER]As I understand it (I've read a lot of stuff on the flexraid forums and others before deciding on snapraid) Flexraid doesn't verify checksums when you update the parity, which means if you get silent errors and you don't check for them and fix them before updating parity, they could propagate into parity, making them impossible to fix... could have changed the last 2 years of course, but I haven't found anything solid to support that... Flexraid doesn't verify checksums when you update the parity, which means if you get silent errors and you don't check for them and fix them before updating parity, they could propagate into parity, making them impossible to fix... In the case of Snapraid it's simple... when you scrub your array, it checks files (more accurately blocks) agains parity and it reports missing files, changed files and bit rot... etc... blocks that have bit rot will be marked as bad.. I myself had bit rot, it got detected by the scrub command and marked as bad... then I fixed it in a few seconds with the fix -E command... Of course to make sure you don't have bit rot (or other degradation of your HDD) you have to regularly run the scrubs command (same with flexraid, there are also other snapshot realtime hybrids that do something like scrub on the fly, HW raid also does something similar) The way snapraid or flexraid works, is that it calulates parity based on the data of the other drives... (very complicated) this is where the difference between flexraid and snapraid comes in... if you don't run scrub or flexraids couterpart regularly, you could have bit rot and when you sync your array, flexraid might calculate new data based on the files that have bitrot... so when you run validate (flexraids version of scrub) it will still detect bit rot, but "Verify" will report no problems, making it impossible to fix it... On snapraid however when you sync your array it will check the files it uses to calculate parity for the new files against old parity first and if it encounters problems (like bit rot) it will stop and mark that block as bad. You can then run fix -E and it will fix the bit rot and you can resume the sync... you so you know, this is a big oversimplification to how snapraid/flexraid works, it's a bit more complicated, but this is just so you understand what happens... I myself did not get snapraid (or any redundancy for that matter) because I was afraid to lose drives, because that is very rare in my experience.... But I did get bitrot a bunch of times, resulting in glitches in videofiles, which is totally annoying, since there is no way to check against that, unles you watch the whole video... snapraid gives me a way to do exactly that and also gives me a way to fix it.. Of course having to option to recover whole drives is awesome as well, if it ever comes to that.. this is btw also the reason a simple backup on anither drive doesn't help much... yes you can see that one file if different than the backup file, but you can't know if the backup file or the original one has bit rot, unless you watch it... (without using any software that also does checksums etc) [/SPOILER] [/QUOTE]
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