September 23, 201015 yr While transferring several files at once, I noticed that the wait % (via top & vmstat) was really high... (see below) Here's a dump from vmstat: r b swpd free buff cache si so bi bo in cs us sy id wa 0 1 0 91444 38708 2908732 0 0 0 1184 1512 3294 0 3 58 39 0 2 0 91908 38732 2908900 0 0 0 1276 1590 3651 0 4 64 32 0 1 0 92172 38732 2908020 0 0 0 1212 1531 3559 0 4 74 22 0 0 0 93676 38736 2906312 0 0 0 526 1040 2357 0 2 52 45 0 0 0 90824 38736 2910532 0 0 0 894 1403 3169 0 2 75 23 0 2 0 90668 38736 2909460 0 0 0 1568 1460 3129 0 4 62 33 0 1 0 87896 38736 2909780 0 0 0 390 1485 3306 0 2 49 49 1 1 0 89212 38736 2910856 0 0 0 2064 1521 3499 0 3 75 21 0 0 0 88948 38740 2911780 0 0 0 936 1559 3543 0 4 60 36 0 2 0 88948 38740 2911756 0 0 0 1380 1487 3664 0 3 68 29 0 1 0 92760 38744 2907356 0 0 0 1230 1541 3644 0 3 71 25 Is there anything that can be done to remove some of waiting? Or is it just the nature of the beast? (EX: If there's writing to disk1, and disk2 is free and usable for a share, write to disk 2?) Or is the 'cache' drive the only alternative? thanks, rwc
September 23, 201015 yr Yup... that is the nature of the beast, because you read a sector, then rewrite that same sector on both the parity disk and the data disk. Queing different disks doesn't matter.... it comes from writing a single disk. Fast disks with larger buffers help, but there is really no way around it. I have wanted to try a caching controller with large (4GB or more) of battery-backed write cache, but haven't gotten there yet. You're lucky... the scheduling changes in the last kernel upgrade made a huge improvement... io-wait used to regularly hover at near 80%.
September 23, 201015 yr Author Eeek...well at least i have the new kernel... I'm using an old board (asus p4p800-e deluxe)...and just found out it doesn't support achi--is this a deal breaker? Would I be able to stream HD (bluray rips) from the server?
September 23, 201015 yr You can stream multiple simultaneous bluray rips at the same time .... streaming HD material is not taxing at all.... even the highest profile is only 40mb/s. You don't have io/wait issues READING from unRAID, only WRITING to protected disks.
September 23, 201015 yr Author 40 megaBITS or megaBytes per second? (For some reason, I thought it was around 130mbs/second for highdef...guess I overestimated that amount?)
September 23, 201015 yr Mbps = mb/s = megabits. MBps = MB/s = megabytes. The maximum bitrate for video in BluRay is upto 40 Mbps (megabits per second) [ http://www.blu-ray.com/faq/#bluray_vs_dvd_comparison ].
Archived
This topic is now archived and is closed to further replies.