internetfriend Posted January 8, 2011 Share Posted January 8, 2011 Based on what I have read, a cache drive speeds up writing to user shares. So for example if I had a "movies" share that was a share of all my movies, I could write to it, it would go to the cache drive, and then write to the share later. The shares spread the data out across the disks. I didn't want that to happen because I like to keep things consolidated and know where X is, so I just have been referencing my data by disk instead of shares. If I want to use a cache drive for this same purpose will it work or is it only for shares? So if I copied X to disk 1, would it be copied to disk 1 correctly at whatever interval at night I chose, or is it specifically only for the shares? Link to comment
Joe L. Posted January 8, 2011 Share Posted January 8, 2011 Based on what I have read, a cache drive speeds up writing to user shares. So for example if I had a "movies" share that was a share of all my movies, I could write to it, it would go to the cache drive, and then write to the share later. The shares spread the data out across the disks. I didn't want that to happen because I like to keep things consolidated and know where X is, so I just have been referencing my data by disk instead of shares. If I want to use a cache drive for this same purpose will it work or is it only for shares? So if I copied X to disk 1, would it be copied to disk 1 correctly at whatever interval at night I chose, or is it specifically only for the shares? You can still use the user-shares, just populate the included and/or excluded disks, OR use a split level of 0 which indicates YOU will create the directories on the disk you desire, and it will only use the disks you create the directories on. Link to comment
SSD Posted January 8, 2011 Share Posted January 8, 2011 Based on what I have read, a cache drive speeds up writing to user shares. So for example if I had a "movies" share that was a share of all my movies, I could write to it, it would go to the cache drive, and then write to the share later. The shares spread the data out across the disks. I didn't want that to happen because I like to keep things consolidated and know where X is, so I just have been referencing my data by disk instead of shares. If I want to use a cache drive for this same purpose will it work or is it only for shares? So if I copied X to disk 1, would it be copied to disk 1 correctly at whatever interval at night I chose, or is it specifically only for the shares? The mover script is designed to work in conjunction with user shares. It is just a shell script and could be modified to write to disk shares, but not how it works OOTB. When used as advertised, the cache disk is not a free lunch for faster writes. What it does is termporarily stores your data on an unprotected disk, and then, overnight, writes the data to the protected array. Not too long ago writes to the protected array were in the 10-12 MB/sec range, while writes to the cache were 40+ MB/sec. So you could do the copy in 1/4 the time. But now, writes to the protected array are in the 30MB/sec range. Writes to cache are still faster, but not nearly the delta of before. And remember you are giving up the protection until sometime in the middle of the night. Given these realities, some users opt to forego cache disks for this purpose and write directly to the protected array. It takes a little longer but you know the data is protected immediately. I have a cache disk and sometimes use it to buffer my writes when I have a lot to do. More often I use it for temporary space and do my writes directly to the array. Link to comment
internetfriend Posted January 8, 2011 Author Share Posted January 8, 2011 Yeah I was around when it was 15MBps transfers in the older UNRAID, but it sounds like I probably don't need one in the end if writes to the cache are only a few MB more. I was assuming it was like 70-80 or whatever the drive tops out at. My download speeds are also at about 30MBps from the server, is that abnormal? Link to comment
tola5 Posted January 13, 2011 Share Posted January 13, 2011 sorry I ask but you sid "writes to the protected array were in the 10-12 MB/sec range" not to long ago when what that I have 4.6 and sata hdd and Gigabit net and copy from the server it 25mb+ but to it are i 8-11 mb are the new 5 ? Link to comment
kizer Posted January 13, 2011 Share Posted January 13, 2011 Yeah I was around when it was 15MBps transfers in the older UNRAID, but it sounds like I probably don't need one in the end if writes to the cache are only a few MB more. I was assuming it was like 70-80 or whatever the drive tops out at. My download speeds are also at about 30MBps from the server, is that abnormal? My all Green WD array does that. It averages between 30-35Mbs on downloads and around 20-25Mbs uploads directly to the array. Link to comment
jeff.lebowski Posted January 13, 2011 Share Posted January 13, 2011 Based on slower writes to the array, does this mean that parity is created for the new files at the same time data is written to the array? Link to comment
Joe L. Posted January 13, 2011 Share Posted January 13, 2011 Based on slower writes to the array, does this mean that parity is created for the new files at the same time data is written to the array? If written to the protected array yes, if written to the cache drive, no. Link to comment
Rajahal Posted January 13, 2011 Share Posted January 13, 2011 Yeah I was around when it was 15MBps transfers in the older UNRAID, but it sounds like I probably don't need one in the end if writes to the cache are only a few MB more. I was assuming it was like 70-80 or whatever the drive tops out at. In my tests the fastest writes to the server I saw were around 73 mb/s, and that was using an SSD as a cache drive. With a normal 7200 rpm drive (actually an older, slower model with an 8 mb cache), I routinely see 60 - 65 mb/s transfers. So these days you can expect that a cache drive will roughly double your write speeds. Worth it for some, not for others. Link to comment
kizer Posted January 13, 2011 Share Posted January 13, 2011 I do all my processing on a windows machine and when I'm done I send it over to the array. Normally a write once and view a lot later. For me speed has never been a real issue since I'm not video editing or anything that requires a lot of bandwidth or disk use. I'm willing to be I'm like most and have never seen the need for a cache disk. What I normally do since my PC is on most of the time I drop files I'm tinkering with into one folder and using windows task manager and a few batch scripts it moves it to the array every 4hours. So I guess in a way I do have a cache drive LOL, but of something a little different. Link to comment
hackztor Posted January 14, 2011 Share Posted January 14, 2011 I tried using cache, but I only had an extra 80gb around. It would fill up after 1-2 blurays and then no more works until its moved. I found it easier just to get ride of the cache. I wished it would auto skip the cache when full. Link to comment
Joe L. Posted January 14, 2011 Share Posted January 14, 2011 I wished it would auto skip the cache when full. It does if you set the min-free space. Otherwise, almost all programs writig to the cache start with an initial empty file and append to it. The initial file always fist but the whole file does not. That is why the min-free field is there. It is in "kb" so set it to about twice the size of a blu-ray rip and the cache will be skipped if that amount of free space is not available. Link to comment
internetfriend Posted January 19, 2011 Author Share Posted January 19, 2011 I ended up deciding to go with a cache drive just for a place to let sabnzbd sickbeard and couchpotato do their work, probably going to skip the user shares though. Link to comment
dgaschk Posted January 19, 2011 Share Posted January 19, 2011 I have a cache drive that I use as a warm spare incase i need to replace a drive and then order a new one. Link to comment
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